System and method for a reverse invitation in a hybrid peer-to-peer environment

ABSTRACT

An improved system and method are disclosed for peer-to-peer communications. In one example, the method enables an endpoint to send a reverse invitation in response to an incoming call. The reverse invitation may be used to set up an alternate communication session rather than maintaining the incoming call.

INCORPORATION BY REFERENCE

The present application incorporates by reference in their entirety U.S. Pat. No. 7,570,636, filed on Aug. 30, 2005, and entitled SYSTEM AND METHOD FOR TRAVERSING A NAT DEVICE FOR PEER-TO-PEER HYBRID COMMUNICATIONS, and U.S. patent application Ser. No. 12/705,925, filed on Feb. 15, 2010, and entitled SYSTEM AND METHOD FOR STRATEGIC ROUTING IN A PEER-TO-PEER ENVIRONMENT.

BACKGROUND

Current packet-based communication networks may be generally divided into peer-to-peer networks and client/server networks. Traditional peer-to-peer networks support direct communication between various endpoints without the use of an intermediary device (e.g., a host or server). Each endpoint may initiate requests directly to other endpoints and respond to requests from other endpoints using credential and address information stored on each endpoint. However, because traditional peer-to-peer networks include the distribution and storage of endpoint information (e.g., addresses and credentials) throughout the network on the various insecure endpoints, such networks inherently have an increased security risk. While a client/server model addresses the security problem inherent in the peer-to-peer model by localizing the storage of credentials and address information on a server, a disadvantage of client/server networks is that the server may be unable to adequately support the number of clients that are attempting to communicate with it. As all communications (even between two clients) must pass through the server, the server can rapidly become a bottleneck in the system.

Accordingly, what is needed are a system and method that addresses these issues.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding, reference is now made to the following description taken in conjunction with the accompanying Drawings in which:

FIG. 1 is a simplified network diagram of one embodiment of a hybrid peer-to-peer system.

FIG. 2 a illustrates one embodiment of an access server architecture that may be used within the system of FIG. 1.

FIG. 2 b illustrates one embodiment of an endpoint architecture that may be used within the system of FIG. 1.

FIG. 2 c illustrates one embodiment of components within the endpoint architecture of FIG. 2 b that may be used for cellular network connectivity.

FIG. 2 d illustrates a traditional softswitch configuration with two endpoints.

FIG. 2 e illustrates a traditional softswitch configuration with three endpoints and a media bridge.

FIG. 2 f illustrates one embodiment of the present disclosure with two endpoints, each of which includes a softswitch.

FIG. 2 g illustrates one embodiment of the present disclosure with three endpoints, each of which includes a softswitch.

FIG. 3 a is a sequence diagram illustrating the interaction of various components of FIG. 2 b when placing a call.

FIG. 3 b is a sequence diagram illustrating the interaction of various components of FIG. 2 b when receiving a call.

FIG. 4 is a sequence diagram illustrating an exemplary process by which an endpoint of FIG. 1 may be authenticated and communicate with another endpoint.

FIG. 5 is a sequence diagram illustrating an exemplary process by which an endpoint of FIG. 1 may determine the status of another endpoint.

FIG. 6 is a sequence diagram illustrating an exemplary process by which an access server of FIG. 1 may aid an endpoint in establishing communications with another endpoint.

FIG. 7 is a sequence diagram illustrating an exemplary process by which an endpoint of FIG. 1 may request that it be added to the buddy list of another endpoint that is currently online.

FIG. 8 is a sequence diagram illustrating an exemplary process by which an endpoint of FIG. 1 may request that it be added to the buddy list of another endpoint that is currently offline.

FIG. 9 is a sequence diagram illustrating an exemplary process by which an endpoint of FIG. 1 may request that it be added to the buddy list of another endpoint that is currently offline before it too goes offline.

FIG. 10 is a simplified diagram of another embodiment of a peer-to-peer system that includes a stateless reflector that may aid an endpoint in traversing a NAT device to communicate with another endpoint.

FIG. 11 is a table illustrating various NAT types and illustrative embodiments of processes that may be used to traverse each NAT type within the system of FIG. 10.

FIG. 12 is a sequence diagram illustrating one embodiment of a process from the table of FIG. 11 in greater detail.

FIG. 13 illustrates one embodiment of a modified packet that may be used within the process of FIG. 12.

FIGS. 14-18 are sequence diagrams that each illustrate an embodiment of a process from the table of FIG. 11 in greater detail.

FIGS. 19A and 19B are simplified diagrams of another embodiment of a peer-to-peer system that includes multiple possible routes between endpoints.

FIG. 20 is a sequence diagram illustrating one embodiment of a process that may be executed by endpoints within the system of FIGS. 19A and 19B.

FIG. 21 is a sequence diagram illustrating one embodiment of steps from the sequence diagram of FIG. 20 in greater detail.

FIG. 22 is a flow chart illustrating one embodiment of a method that may be executed by an endpoint within the system of FIGS. 19A and 19B.

FIGS. 23A and 23B are simplified diagrams of another embodiment of a peer-to-peer system that includes a tunneling server and multiple possible routes between endpoints.

FIG. 24 is a sequence diagram illustrating one embodiment of a process that may be executed by endpoints within the system of FIGS. 23A and 23B.

FIG. 25 is a simplified diagram of another embodiment of a peer-to-peer environment that may use a virtual endpoint to represent a device in a peer-to-peer network.

FIGS. 26-29 are sequence diagrams illustrating embodiments of various processes that may be executed within the environment of FIG. 25.

FIG. 30 is a simplified diagram of an embodiment of an environment in which a reverse invitation may occur.

FIG. 31 is a sequence diagram illustrating one embodiment of a process that may be executed by endpoints within the environment of FIG. 30.

FIG. 32 is a sequence diagram illustrating another embodiment of a process that may be executed by endpoints within the environment of FIG. 30.

FIG. 33 is a flow chart illustrating one embodiment of a method that may be executed by an endpoint within the environment of FIG. 30.

FIG. 34 is a flow chart illustrating another embodiment of a method that may be executed by an endpoint within the environment of FIG. 30.

FIG. 35 is a sequence diagram illustrating another embodiment of a process that may be executed by endpoints within the environment of FIG. 30.

FIGS. 36A and 36B are simplified diagrams of another embodiment of an environment in which a reverse invitation may occur.

FIGS. 37A and 37B are simplified diagrams of an embodiment of another environment in which a reverse invitation may occur.

FIG. 38 is a simplified diagram of one embodiment of a computer system that may be used in embodiments of the present disclosure.

DETAILED DESCRIPTION

The present disclosure is directed to a system and method for peer-to-peer hybrid communications. It is understood that the following disclosure provides many different embodiments or examples. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Referring to FIG. 1, one embodiment of a peer-to-peer hybrid system 100 is illustrated. The system 100 includes an access server 102 that is coupled to endpoints 104 and 106 via a packet network 108. Communication between the access server 102, endpoint 104, and endpoint 106 is accomplished using predefined and publicly available (i.e., non-proprietary) communication standards or protocols (e.g., those defined by the Internet Engineering Task Force (IETF) or the International Telecommunications Union-Telecommunications Standard Sector (ITU-T)). For example, signaling communications (e.g., session setup, management, and teardown) may use a protocol such as the Session Initiation Protocol (SIP), while actual data traffic may be communicated using a protocol such as the Real-time Transport Protocol (RTP). As will be seen in the following examples, the use of standard protocols for communication enables the endpoints 104 and 106 to communicate with any device that uses the same standards. The communications may include, but are not limited to, voice calls, instant messages, audio and video, emails, and any other type of resource transfer, where a resource represents any digital data. In the following description, media traffic is generally based on the user datagram protocol (UDP), while authentication is based on the transmission control protocol/internet protocol (TCP/IP). However, it is understood that these are used for purposes of example and that other protocols may be used in addition to or instead of UDP and TCP/IP.

Connections between the access server 102, endpoint 104, and endpoint 106 may include wireline and/or wireless communication channels. In the following description, it is understood that the term “direct” means that there is no endpoint or access server in the communication channel(s) between the endpoints 104 and 106, or between either endpoint and the access server. Accordingly, the access server 102, endpoint 104, and endpoint 106 are directly connected even if other devices (e.g., routers, firewalls, and other network elements) are positioned between them. In addition, connections to endpoints, locations, or services may be subscription based, with an endpoint only having access if the endpoint has a current subscription. Furthermore, the following description may use the terms “user” and “endpoint” interchangeably, although it is understood that a user may be using any of a plurality of endpoints. Accordingly, if an endpoint logs in to the network, it is understood that the user is logging in via the endpoint and that the endpoint represents the user on the network using the user's identity.

The access server 102 stores profile information for a user, a session table to track what users are currently online, and a routing table that matches the address of an endpoint to each online user. The profile information includes a “buddy list” for each user that identifies other users (“buddies”) that have previously agreed to communicate with the user. Online users on the buddy list will show up when a user logs in, and buddies who log in later will directly notify the user that they are online (as described with respect to FIG. 4). The access server 102 provides the relevant profile information and routing table to each of the endpoints 104 and 106 so that the endpoints can communicate directly with one another. Accordingly, in the present embodiment, one function of the access server 102 is to serve as a storage location for information needed by an endpoint in order to communicate with other endpoints and as a temporary storage location for requests, voicemails, etc., as will be described later in greater detail.

With additional reference to FIG. 2 a, one embodiment of an architecture 200 for the access server 102 of FIG. 1 is illustrated. The architecture 200 includes functionality that may be provided by hardware and/or software, and that may be combined into a single hardware platform or distributed among multiple hardware platforms. For purposes of illustration, the access server in the following examples is described as a single device, but it is understood that the term applies equally to any type of environment (including a distributed environment) in which at least a portion of the functionality attributed to the access server is present.

In the present example, the architecture includes web services 202 (e.g., based on functionality provided by XML, SOAP, .NET, MONO), web server 204 (using, for example, Apache or IIS), and database 206 (using, for example, mySQL or SQLServer) for storing and retrieving routing tables 208, profiles 210, and one or more session tables 212. Functionality for a STUN (Simple Traversal of UDP through NATs (Network Address Translation)) server 214 is also present in the architecture 200. As is known, STUN is a protocol for assisting devices that are behind a NAT firewall or router with their packet routing. The architecture 200 may also include a redirect server 216 for handling requests originating outside of the system 100. One or both of the STUN server 214 and redirect server 216 may be incorporated into the access server 102 or may be a standalone device. In the present embodiment, both the server 204 and the redirect server 216 are coupled to the database 206.

Referring to FIG. 2 b, one embodiment of an architecture 250 for the endpoint 104 (which may be similar or identical to the endpoint 106) of FIG. 1 is illustrated. It is understood that that term “endpoint” may refer to many different devices having some or all of the described functionality, including a computer, a VoIP telephone, a personal digital assistant, a cellular phone, or any other device having an IP stack upon which the needed protocols may be run. Such devices generally include a network interface, a controller coupled to the network interface, a memory coupled to the controller, and instructions executable by the controller and stored in the memory for performing the functions described in the present application. Data needed by an endpoint may also be stored in the memory. The architecture 250 includes an endpoint engine 252 positioned between a graphical user interface (GUI) 254 and an operating system 256. The GUI 254 provides user access to the endpoint engine 252, while the operating system 256 provides underlying functionality, as is known to those of skill in the art.

The endpoint engine 252 may include multiple components and layers that support the functionality required to perform the operations of the endpoint 104. For example, the endpoint engine 252 includes a softswitch 258, a management layer 260, an encryption/decryption module 262, a feature layer 264, a protocol layer 266, a speech-to-text engine 268, a text-to-speech engine 270, a language conversion engine 272, an out-of-network connectivity module 274, a connection from other networks module 276, a p-commerce (e.g., peer commerce) engine 278 that includes a p-commerce agent and a p-commerce broker, and a cellular network interface module 280.

Each of these components/layers may be further divided into multiple modules. For example, the softswitch 258 includes a call control module, an instant messaging (IM) control module, a resource control module, a CALEA (Communications Assistance to Law Enforcement Act) agent, a media control module, a peer control module, a signaling agent, a fax control module, and a routing module.

The management layer 260 includes modules for presence (i.e., network presence), peer management (detecting peers and notifying peers of being online), firewall management (navigation and management), media management, resource management, profile management, authentication, roaming, fax management, and media playback/recording management.

The encryption/decryption module 262 provides encryption for outgoing packets and decryption for incoming packets. In the present example, the encryption/decryption module 262 provides application level encryption at the source, rather than at the network. However, it is understood that the encryption/decryption module 262 may provide encryption at the network in some embodiments.

The feature layer 264 provides support for various features such as voice, video, IM, data, voicemail, file transfer, file sharing, class 5 features, short message service (SMS), interactive voice response (IVR), faxes, and other resources. The protocol layer 266 includes protocols supported by the endpoint, including SIP, HTTP, HTTPS, STUN, RTP, SRTP, and ICMP. It is understood that these are examples only, and that fewer or more protocols may be supported.

The speech-to-text engine 268 converts speech received by the endpoint (e.g., via a microphone or network) into text, the text-to-speech engine 270 converts text received by the endpoint into speech (e.g., for output via a speaker), and the language conversion engine 272 may be configured to convert inbound or outbound information (text or speech) from one language to another language. The out-of-network connectivity module 274 may be used to handle connections between the endpoint and external devices (as described with respect to FIG. 12), and the connection from other networks module 276 handles incoming connection attempts from external devices. The cellular network interface module 280 may be used to interact with a wireless network.

With additional reference to FIG. 2 c, the cellular network interface module 280 is illustrated in greater detail. Although not shown in FIG. 2 b, the softswitch 258 of the endpoint architecture 250 includes a cellular network interface for communication with the cellular network interface module 280. In addition, the cellular network interface module 280 includes various components such as a call control module, a signaling agent, a media manager, a protocol stack, and a device interface. It is noted that these components may correspond to layers within the endpoint architecture 250 and may be incorporated directly into the endpoint architecture in some embodiments.

Referring to FIG. 2 d, a traditional softswitch architecture is illustrated with two endpoints 282 and 284, neither of which includes a softswitch. In the present example, an external softswitch 286 maintains a first signaling leg (dotted line) with the endpoint 282 and a second signaling leg (dotted line) with the endpoint 284. The softswitch 286 links the two legs to pass signaling information between the endpoints 282 and 284. Media traffic (solid lines) may be transferred between the endpoints 282 and 284 via a media gateway 287.

With additional reference to FIG. 2 e, the traditional softswitch architecture of FIG. 2 d is illustrated with a third endpoint 288 that also does not include a softswitch. The external softswitch 286 now maintains a third signaling leg (dotted line) with the endpoint 288. In the present example, a conference call is underway. However, as none of the endpoints includes a softswitch, a media bridge 290 connected to each endpoint is needed for media traffic. Accordingly, each endpoint has at most two concurrent connections—one with the softswitch for signaling and another with the media bridge for media traffic.

Referring to FIG. 2 f, in one embodiment, unlike the traditional architecture of FIGS. 2 d and 2 e, two endpoints (e.g., the endpoints 104 and 106 of FIG. 1) each include a softswitch (e.g., the softswitch 258 of FIG. 2 b). Each endpoint is able to establish and maintain both signaling and media traffic connections (both virtual and physical legs) with the other endpoint. Accordingly, no external softswitch is needed, as this model uses a distributed softswitch method to handle communications directly between the endpoints.

With additional reference to FIG. 2 g, the endpoints 104 and 106 are illustrated with another endpoint 292 that also contains a softswitch. In this example, a conference call is underway with the endpoint 104 acting as the host. To accomplish this, the softswitch contained in the endpoint 104 enables the endpoint 104 to support direct signaling and media traffic connections with the endpoint 292. The endpoint 104 can then forward media traffic from the endpoint 106 to the endpoint 292 and vice versa. Accordingly, the endpoint 104 may support multiple connections to multiple endpoints and, as in FIG. 2 f, no external softswitch is needed.

Referring again to FIG. 2 b, in operation, the softswitch 258 uses functionality provided by underlying layers to handle connections with other endpoints and the access server 102, and to handle services needed by the endpoint 104. For example, as is described below in greater detail with respect to FIGS. 3 a and 3 b, incoming and outgoing calls may utilize multiple components within the endpoint architecture 250.

Referring to FIG. 3 a, a sequence diagram 300 illustrates an exemplary process by which the endpoint 104 may initiate a call to the endpoint 106 using various components of the architecture 250. Prior to step 302, a user (not shown) initiates a call via the GUI 254. In step 302, the GUI 254 passes a message to the call control module (of the softswitch 258) to make the call. The call control module contacts the peer control module (softswitch 258) in step 304, which detects the peer (if not already done), goes to the routing table (softswitch 258) for the routing information, and performs similar operations. It is understood that not all interactions are illustrated. For example, the peer control module may utilize the peer management module (of the management layer 260) for the peer detection. The call control module then identifies a route for the call in step 306, and sends message to the SIP protocol layer (of the protocol layer 266) to make the call in step 308. In step 310, the outbound message is encrypted (using the encryption/decryption module 262) and the message is sent to the network via the OS 256 in step 312.

After the message is sent and prior to receiving a response, the call control module instructs the media control module (softswitch 258) to establish the needed near-end media in step 314. The media control module passes the instruction to the media manager (of the management layer 260) in step 316, which handles the establishment of the near-end media.

With additional reference to FIG. 3 b, the message sent by the endpoint 104 in step 312 (FIG. 3 a) is received by the endpoint 106 and passed from the OS to the SIP protocol layer in step 352. The message is decrypted in step 354 and the call is offered to the call control module in step 356. The call control module notifies the GUI of an incoming call in step 358 and the GUI receives input identifying whether the call is accepted or rejected (e.g., by a user) in step 360. In the present example, the call is accepted and the GUI passes the acceptance to the call control module in step 362. The call control module contacts the peer control module in step 364, which identifies a route to the calling endpoint and returns the route to the call control module in step 366. In steps 368 and 370, the call control module informs the SIP protocol layer that the call has been accepted and the message is encrypted using the encryption/decryption module. The acceptance message is then sent to the network via the OS in step 372.

In the present example, after the call control module passes the acceptance message to the SIP protocol layer, other steps may occur to prepare the endpoint 106 for the call. For example, the call control module instructs the media control module to establish near-end media in step 374, and the media control module instructs the media manager to start listening to incoming media in step 376. The call control module also instructs the media control module to establish far-end media (step 378), and the media control module instructs the media manager to start transmitting audio in step 380.

Returning to FIG. 3 a, the message sent by the endpoint 106 (step 372) is received by the OS and passed on to the SIP protocol layer in step 318 and decrypted in step 320. The message (indicating that the call has been accepted) is passed to the call control module in step 322 and from there to the GUI in step 324. The call control module then instructs the media control module to establish far-end media in step 326, and the media control module instructs the media manager to start transmitting audio in step 328.

The following figures are sequence diagrams that illustrate various exemplary functions and operations by which the access server 102 and the endpoints 104 and 106 may communicate. It is understood that these diagrams are not exhaustive and that various steps may be excluded from the diagrams to clarify the aspect being described.

Referring to FIG. 4 (and using the endpoint 104 as an example), a sequence diagram 400 illustrates an exemplary process by which the endpoint 104 may authenticate with the access server 102 and then communicate with the endpoint 106. As will be described, after authentication, all communication (both signaling and media traffic) between the endpoints 104 and 106 occurs directly without any intervention by the access server 102. In the present example, it is understood that neither endpoint is online at the beginning of the sequence, and that the endpoints 104 and 106 are “buddies.” As described above, buddies are endpoints that have both previously agreed to communicate with one another.

In step 402, the endpoint 104 sends a registration and/or authentication request message to the access server 102. If the endpoint 104 is not registered with the access server 102, the access server will receive the registration request (e.g., user ID, password, and email address) and will create a profile for the endpoint (not shown). The user ID and password will then be used to authenticate the endpoint 104 during later logins. It is understood that the user ID and password may enable the user to authenticate from any endpoint, rather than only the endpoint 104.

Upon authentication, the access server 102 updates a session table residing on the server to indicate that the user ID currently associated with the endpoint 104 is online. The access server 102 also retrieves a buddy list associated with the user ID currently used by the endpoint 104 and identifies which of the buddies (if any) are online using the session table. As the endpoint 106 is currently offline, the buddy list will reflect this status. The access server 102 then sends the profile information (e.g., the buddy list) and a routing table to the endpoint 104 in step 404. The routing table contains address information for online members of the buddy list. It is understood that steps 402 and 404 represent a make and break connection that is broken after the endpoint 104 receives the profile information and routing table.

In steps 406 and 408, the endpoint 106 and access server 102 repeat steps 402 and 404 as described for the endpoint 104. However, because the endpoint 104 is online when the endpoint 106 is authenticated, the profile information sent to the endpoint 106 will reflect the online status of the endpoint 104 and the routing table will identify how to directly contact it. Accordingly, in step 410, the endpoint 106 sends a message directly to the endpoint 104 to notify the endpoint 104 that the endpoint 106 is now online. This also provides the endpoint 104 with the address information needed to communicate directly with the endpoint 106. In step 412, one or more communication sessions may be established directly between the endpoints 104 and 106.

Referring to FIG. 5, a sequence diagram 500 illustrates an exemplary process by which authentication of an endpoint (e.g., the endpoint 104) may occur. In addition, after authentication, the endpoint 104 may determine whether it can communicate with the endpoint 106. In the present example, the endpoint 106 is online when the sequence begins.

In step 502, the endpoint 104 sends a request to the STUN server 214 of FIG. 2. As is known, the STUN server determines an outbound IP address (e.g., the external address of a device (i.e., a firewall, router, etc.) behind which the endpoint 104 is located), an external port, and a type of NAT used by the device. The type of NAT may be, for example, full cone, restricted cone, port restricted cone, or symmetric, each of which is discussed later in greater detail with respect to FIG. 10. The STUN server 214 sends a STUN response back to the endpoint 104 in step 504 with the collected information about the endpoint 104.

In step 506, the endpoint 104 sends an authentication request to the access server 102. The request contains the information about endpoint 104 received from the STUN server 214. In step 508, the access server 102 responds to the request by sending the relevant profile and routing table to the endpoint 104. The profile contains the external IP address, port, and NAT type for each of the buddies that are online

In step 510, the endpoint 104 sends a message to notify the endpoint 106 of its online status (as the endpoint 106 is already online) and, in step 512, the endpoint 104 waits for a response. After the expiration of a timeout period within which no response is received from the endpoint 106, the endpoint 104 will change the status of the endpoint 106 from “online” (as indicated by the downloaded profile information) to “unreachable.” The status of a buddy may be indicated on a visual buddy list by the color of an icon associated with each buddy. For example, when logging in, online buddies may be denoted by a blue icon and offline buddies may be denoted by a red icon. If a response to a notify message is received for a buddy, the icon representing that buddy may be changed from blue to green to denote the buddy's online status. If no response is received, the icon remains blue to indicate that the buddy is unreachable. Although not shown, a message sent from the endpoint 106 and received by the endpoint 104 after step 514 would indicate that the endpoint 106 is now reachable and would cause the endpoint 104 to change the status of the endpoint 106 to online Similarly, if the endpoint 104 later sends a message to the endpoint 106 and receives a response, then the endpoint 104 would change the status of the endpoint 106 to online.

It is understood that other embodiments may implement alternate NAT traversal techniques. For example, a single payload technique may be used in which TCP/IP packets are used to traverse a UDP restricted firewall or router. Another example includes the use of a double payload in which a UDP packet is inserted into a TCP/IP packet. Furthermore, it is understood that protocols other than STUN may be used. For example, protocols such as Internet Connectivity Establishment (ICE) or Traversal Using Relay NAT (TURN) may be used.

Referring to FIG. 6, a sequence diagram 600 illustrates an exemplary process by which the access server 102 may aid the endpoint 104 in establishing communications with the endpoint 106 (which is a buddy). After rendering aid, the access server 102 is no longer involved and the endpoints may communicate directly. In the present example, the endpoint 106 is behind a NAT device that will only let a message in (towards the endpoint 106) if the endpoint 106 has sent a message out. Unless this process is bypassed, the endpoint 104 will be unable to connect to the endpoint 106. For example, the endpoint 104 will be unable to notify the endpoint 106 that it is now online

In step 602, the endpoint 106 sends a request to the STUN server 214 of FIG. 2. As described previously, the STUN server determines an outbound IP address, an external port, and a type of NAT for the endpoint 106. The STUN server 214 sends a STUN response back to the endpoint 106 in step 604 with the collected information about the endpoint 106. In step 606, the endpoint 106 sends an authentication request to the access server 102. The request contains the information about endpoint 106 received from the STUN server 214. In step 608, the access server 102 responds to the request by sending the relevant profile and routing table to the endpoint 106. In the present example, the access server 102 identifies the NAT type associated with the endpoint 106 as being a type that requires an outbound packet to be sent before an inbound packet is allowed to enter. Accordingly, the access server 102 instructs the endpoint 106 to send periodic messages to the access server 102 to establish and maintain a pinhole through the NAT device. For example, the endpoint 106 may send a message prior to the timeout period of the NAT device in order to reset the timeout period. In this manner, the pinhole may be kept open indefinitely.

In steps 612 and 614, the endpoint 104 sends a STUN request to the STUN server 214 and the STUN server responds as previously described. In step 616, the endpoint 104 sends an authentication request to the access server 102. The access server 102 retrieves the buddy list for the endpoint 104 and identifies the endpoint 106 as being associated with a NAT type that will block communications from the endpoint 104. Accordingly, in step 618, the access server 102 sends an assist message to the endpoint 106. The assist message instructs the endpoint 106 to send a message to the endpoint 104, which opens a pinhole in the NAT device for the endpoint 104. For security purposes, as the access server 102 has the STUN information for the endpoint 104, the pinhole opened by the endpoint 106 may be specifically limited to the endpoint associated with the STUN information. Furthermore, the access server 102 may not request such a pinhole for an endpoint that is not on the buddy list of the endpoint 106.

The access server 104 sends the profile and routing table to the endpoint 104 in step 620. In step 622, the endpoint 106 sends a message (e.g., a ping packet) to the endpoint 104. The endpoint 104 may then respond to the message and notify the endpoint 106 that it is now online. If the endpoint 106 does not receive a reply from the endpoint 104 within a predefined period of time, it may close the pinhole (which may occur simply by not sending another message and letting the pinhole time out). Accordingly, the difficulty presented by the NAT device may be overcome using the assist message, and communications between the two endpoints may then occur without intervention by the access server 102.

Referring to FIG. 7, a sequence diagram 700 illustrates an exemplary process by which the endpoint 106 may request that it be added to the endpoint 104′s buddy list. In the present example, the endpoints 104 and 106 both remain online during the entire process.

In step 702, the endpoint 104 sends a registration and/or authentication request message to the access server 102 as described previously. Upon authentication, the access server 102 updates a session table residing on the server to indicate that the user ID currently associated with the endpoint 104 is online. The access server 102 also retrieves a buddy list associated with the user ID currently used by the endpoint 104 and identifies which of the buddies (if any) are online using the session table. As the endpoint 106 is not currently on the buddy list, it will not be present. The access server 102 then sends the profile information and a routing table to the endpoint 104 in step 704.

In steps 706 and 708, the endpoint 106 and access server 102 repeat steps 702 and 704 as described for the endpoint 104. The profile information sent by the access server 102 to the endpoint 106 will not include the endpoint 104 because the two endpoints are not buddies.

In step 710, the endpoint 106 sends a message to the access server 102 requesting that the endpoint 104 be added to its buddy list. The access server 102 determines that the endpoint 104 is online (e.g., using the session table) in step 712 and sends the address for the endpoint 104 to the endpoint 106 in step 714. In step 716, the endpoint 106 sends a message directly to the endpoint 104 requesting that the endpoint 106 be added to its buddy list. The endpoint 104 responds to the endpoint 106 in step 718 with either permission or a denial, and the endpoint 104 also updates the access server 102 with the response in step 720. For example, if the response grants permission, then the endpoint 104 informs the access server 102 so that the access server can modify the profile of both endpoints to reflect the new relationship. It is understood that various other actions may be taken. For example, if the endpoint 104 denies the request, then the access server 102 may not respond to another request by the endpoint 106 (with respect to the endpoint 104) until a period of time has elapsed.

It is understood that many different operations may be performed with respect to a buddy list. For example, buddies may be deleted, blocked/unblocked, buddy status may be updated, and a buddy profile may be updated. For block/unblock, as well as status and profile updates, a message is first sent to the access server 102 by the endpoint requesting the action (e.g., the endpoint 104). Following the access server 102 update, the endpoint 104 sends a message to the peer being affected by the action (e.g., the endpoint 106).

Buddy deletion may be handled as follows. If the user of the endpoint 104 wants to delete a contact on a buddy list currently associated with the online endpoint 106, the endpoint 104 will first notify the access server 102 that the buddy is being deleted. The access server 102 then updates the profile of both users so that neither buddy list shows the other user as a buddy. Note that, in this instance, a unilateral action by one user will alter the profile of the other user. The endpoint 104 then sends a message directly to the endpoint 106 to remove the buddy (the user of the endpoint 104) from the buddy list of the user of endpoint 106 in real time. Accordingly, even though the user is online at endpoint 106, the user of the endpoint 104 will be removed from the buddy list of the endpoint 106.

Referring to FIG. 8, a sequence diagram 800 illustrates an exemplary process by which the endpoint 106 may request that it be added to the endpoint 104′s buddy list. In the present example, the endpoint 104 is not online until after the endpoint 106 has made its request.

In step 802, the endpoint 106 sends a registration and/or authentication request message to the access server 102 as described previously. Upon authentication, the access server 102 updates a session table residing on the server to indicate that the user ID currently associated with the endpoint 106 is online. The access server 102 also retrieves a buddy list associated with the user ID currently used by the endpoint 106 and identifies which of the buddies (if any) are online using the session table. The access server 102 then sends the profile information and a routing table to the endpoint 106 in step 804.

In step 806, the endpoint 106 sends a message to the access server 102 requesting that the endpoint 104 be added to its buddy list. The access server 102 determines that the endpoint 104 is offline in step 808 and temporarily stores the request message in step 810. In steps 812 and 814, the endpoint 104 and access server 102 repeat steps 802 and 804 as described for the endpoint 106. However, when the access server 102 sends the profile information and routing table to the endpoint 104, it also sends the request by the endpoint 106 (including address information for the endpoint 106).

In step 816, the endpoint 104 responds directly to the endpoint 106 with either permission or a denial. The endpoint 104 then updates the access server 102 with the result of the response in step 818 and also instructs the access server to delete the temporarily stored request.

Referring to FIG. 9, a sequence diagram 900 illustrates an exemplary process by which the endpoint 106 may request that it be added to the endpoint 104′s buddy list. In the present example, the endpoint 104 is not online until after the endpoint 106 has made its request, and the endpoint 106 is not online to receive the response by endpoint 104.

In step 902, the endpoint 106 sends a registration and/or authentication request message to the access server 102 as described previously. Upon authentication, the access server 102 updates a session table residing on the server to indicate that the user ID currently associated with the endpoint 106 is online. The access server 102 also retrieves a buddy list associated with the user ID currently used by the endpoint 106 and identifies which of the buddies (if any) are online using the session table. The access server 102 then sends the profile information and a routing table to the endpoint 106 in step 904.

In step 906, the endpoint 106 sends a message to the access server 102 requesting that the endpoint 104 be added to its buddy list. The access server 102 determines that the endpoint 104 is offline in step 908 and temporarily stores the request message in step 910. In step 912, the endpoint 106 notifies the access server 102 that it is going offline.

In steps 914 and 916, the endpoint 104 and access server 102 repeat steps 902 and 904 as described for the endpoint 106. However, when the access server 102 sends the profile information and routing table to the endpoint 104, it also sends the request by the endpoint 106. Endpoint 104 sends its response to the access server 102 in step 918 and also instructs the access server to delete the temporarily stored request. After the endpoint 106′s next authentication process, its profile information will include endpoint 104 as a buddy (assuming the endpoint 104 granted permission).

Referring to FIG. 10, in one embodiment, a system 1000 includes a stateless reflector 1002 and two endpoints 104 and 106, such as the endpoints 104 and 106 described with respect to the preceding figures. In the present example, each of the endpoints 104 and 106 are behind a device 1004, 1006, respectively, that monitors and regulates communication with its respective endpoint. Each device 1004, 1006 in the present example is a firewall having NAT technology. As described previously, a NAT device may present an obstacle in establishing a peer-to-peer connection because it may not allow unsolicited messages (e.g., it may require a packet to be sent out through the NAT device before allowing a packet in). For example, the NAT device 1006 positioned between the endpoint 106 and network 108 may only let a message in (towards the endpoint 106) if the endpoint 106 has sent a message out. Unless the NAT device's status is shifted from not soliciting messages from the endpoint 104 to soliciting messages from the endpoint 104, the endpoint 104 will be unable to connect to the endpoint 106. For example, the endpoint 104 will be unable to notify the endpoint 106 that it is now online.

As will be described below in greater detail, the stateless reflector 1002 is configured to receive one or more packets from an endpoint and reflect the packet to another endpoint after modifying information within the packet. This reflection process enables the endpoints 104 and 106 to communicate regardless of the presence and type of the NAT devices 1004 and 1006. The stateless reflector 1002 is stateless because state information (e.g., information relating to how an endpoint is to connect with other endpoints) is stored by the endpoints, as described previously. Accordingly, the stateless reflector 1002 processes header information contained within a packet without access to other information about the network or endpoints, such as the database 206 of FIG. 2 a. Although only one stateless reflector 1002 is illustrated in FIG. 10, it is understood that multiple stateless reflectors may be provided, and that the endpoints 104 and 106 may each use a different stateless reflector. For example, an endpoint may be configured to use a particular stateless reflector or may select a stateless reflector based on location, NAT type, etc.

Although each endpoint 104, 106 is shown with a separate NAT device 1004, 1006, it is understood that multiple endpoints may be connected to the network 108 via a single NAT device. For example, a LAN may access the network 108 via a single NAT device, and all communications between the endpoints connected to the LAN and the network 108 must pass through the NAT device. However, communications between the endpoints within the LAN itself may occur directly, as previously described, because the endpoints are not communicating through the NAT device. Furthermore, if one of the endpoints 104 or 106 does not have a NAT device, then communications with that endpoint may occur directly as described above even if the endpoints are not in the same network.

Each NAT device 1004 and 1006 includes an internal IP address (on the side coupled to the endpoint 104 for the NAT device 1004 and the side coupled to the endpoint 106 for the NAT device 1006) and an external IP address (on the side coupled to the network 108 for both NAT devices). Each connection is also associated with an internal port and an external port. Therefore, each connection includes both internal IP address/port information and external IP address/port information.

Generally, a NAT device may be defined as full cone, restricted cone, port restricted cone, or symmetric. A full cone NAT is one where all requests from the same internal IP address and port are mapped to the same external IP address and port. Therefore, any external host can send a packet to the internal host by sending a packet to the mapped external address.

A restricted cone NAT is one where all requests from the same internal IP address and port are mapped to the same external IP address and port. Unlike a full cone NAT, an external host can send a packet to the internal host only if the internal host has previously sent a packet to the external host's IP address.

A port restricted cone NAT is like a restricted cone NAT, but the restriction includes port numbers. More specifically, an external host can send a packet with source IP address X and source port P to the internal host only if the internal host has previously sent a packet to the external host at IP address X and port P.

A symmetric NAT is one where all requests from the same internal IP address and port to a specific destination IP address and port are mapped to the same external IP address and port. If the same host sends a packet with the same source address and port, but to a different destination, a different mapping is used. Only the external host that receives a packet can send a UDP packet back to the internal host.

Referring to FIG. 11, a table 1100 illustrates one embodiment of a communication structure that may be used to traverse one or both of the NAT devices 1004 and 1006 of FIG. 10. The table 1100 provides five possible types for the NAT devices 1004 and 1006: no NAT, full cone, restricted cone, port restricted cone, and symmetric. It is understood that “no NAT” may indicate that no device is there, that a device is there but does not include NAT functionality, or that a device is there and any NAT functionality within the device has been disabled. Either of the NAT devices 1004 and 1006 may be on the originating side of the communication or on the terminating side. For purposes of convenience, the endpoint 104 is the originating endpoint and the endpoint 106 is the terminating endpoint, and the NAT device 1004 is the originating NAT device and the NAT device 1006 is the terminating NAT device. It is understood that the terms “endpoint” and “NAT device” may be used interchangeably in some situations. For example, sending a packet to the endpoint 106 generally involves sending a packet to the NAT device 1006, which then forwards the packet to the endpoint 106 after performing the network address translation. However, the following discussion may simply refer to sending a packet to the endpoint 106 and it will be understood that the packet must traverse the NAT device 1006.

As illustrated by the table 1100, there are twenty-five possible pairings of NAT types and establishing communication between different NAT types may require different steps. For purposes of convenience, these twenty-five pairings may be grouped based on the required steps. For example, if the originating NAT type is no NAT, full cone, restricted cone, or port restricted cone, then the originating NAT can establish communication directly with a terminating NAT type of either no NAT or full cone.

If the originating NAT type is no NAT or full cone, then the originating NAT can establish communications with a terminating NAT type of either restricted cone or port restricted cone only after using the stateless reflector 1002 to reflect a packet. This process is described below with respect to FIG. 12.

Referring to FIG. 12, the endpoint 104 wants to inform the endpoint 106, which is already logged on, that the endpoint 104 has logged on. The NAT device 1004 is either a no NAT or a full cone type and the NAT device 1006 is either a restricted cone or a port restricted cone type. Accordingly, the endpoint 104 wants to send a message to the endpoint 106, but has not received a message from the endpoint 106 that would allow the endpoint 104 to traverse the NAT device 1006.

Although not shown in FIG. 12, prior to or during authentication, the endpoints 104 and 106 both sent a request to a STUN server (e.g., the STUN server 214 of FIG. 2) (not shown in FIG. 10). The STUN server determined an outbound IP address, an external port, and a type of NAT for the endpoints 104 and 106 (in this example, for the NAT devices 1004 and 1006). The STUN server 214 then sent a STUN response back to the endpoints 104 and 106 with the collected information. The endpoints 104 and 106 then sent an authentication request to an access server (e.g., the access server 102 of FIG. 1) (not shown in FIG. 10). The request contains the information about endpoints 104 and 106 received from the STUN server 214. The access server 102 responds to the requests by sending the relevant profile and routing table to the endpoints 104 and 106. In addition, each NAT device 1004 and 1006 may have a pinhole to the STUN server 214.

In the present example, the NAT device 1004 has an external address/port of 1.1.1.1:1111 and the NAT device 1006 has an external address/port of 2.2.2.2:2222. The STUN server 214 has an address/port of 3.3.3.3:3333 and the stateless reflector has an address/port of 4.4.4.4:4444. It is understood that the STUN server and/or stateless reflector 1002 may have multiple addresses/ports.

Referring to FIG. 12 and with additional reference to FIG. 13, in step 1202, the endpoint 104 sends a packet to the stateless reflector 1002. The packet contains header information identifying the source as the endpoint 104 (or rather, the external IP address of the NAT device 1004) and the destination as the stateless reflector 1002. The packet also contains custom or supplemental header information identifying the source as the STUN server 214 and the destination as the endpoint 106. Accordingly, the IP/UDP header of the packet sent from the endpoint 104 (via the NAT device 1004) identifies its source as 1.1.1.1:1111 and its destination as 4.4.4.4:4444.

In step 1204, the stateless reflector 1002 modifies the packet header by replacing the IP/UDP header with the source and destination from the custom header. In the present example, the stateless reflector 1002 will modify the IP/UDP header to identify the packet's source as 3.3.3.3:3333 and its destination as 2.2.2.2:2222. Identifying the packet's source as the STUN server 214 enables the stateless reflector 1002 to send the packet through the pinhole in the NAT device 1006 that was created when the endpoint 106 logged on. After modifying the header, the stateless reflector 1002 sends the packet to the endpoint 106 via the NAT device 1006 in step 1206.

In step 1208, the endpoint 106 sends an acknowledgement (e.g., a 200 OK) directly to the endpoint 104. The address of the endpoint 104 is contained within the payload of the packet. The endpoint 106 is able to send the acknowledgement directly because the NAT device 1004 is either a no NAT or a full cone type. Because the endpoint 106 has opened a pinhole through the restricted or port restricted NAT device 1006 to the endpoint 104 by sending a message to the endpoint 104, the endpoint 104 is now able to communicate directly with the endpoint 106, as indicated by step 1210.

Referring again to table 1100 of FIG. 11, if the originating NAT type is either a no NAT type or a full cone type, then the originating NAT can establish communications with a terminating NAT type that is symmetric only after using the stateless reflector 1002 to reflect a packet and then performing a port capture. This process is described below with respect to FIG. 14.

Referring to FIG. 14, steps 1402, 1404, 1406, and 1408 are similar to the reflection process described with respect to FIG. 12, and will not be described in detail in the present example. Because the terminating NAT type is symmetric, the originating NAT needs the port of the terminating NAT in order to send packets through the NAT device 1006. Accordingly, in step 1410, the endpoint 104 will capture the external port used by the NAT device 1006 to send the acknowledgement in step 1408. This port, along with the address of the NAT device 1006, may then be used when communicating with the endpoint 106, as indicated by step 1412.

Referring again to table 1100 of FIG. 11, if the originating NAT type is either a restricted cone type or a port restricted cone type, then the originating NAT can establish communications with a terminating NAT type that is either restricted or port restricted by using a fake packet and then using the stateless reflector 1002 to reflect a packet. This process is described below with respect to FIG. 15.

Referring to FIG. 15, in step 1502, the endpoint 104 sends a fake packet to the endpoint 106. Because the originating NAT type is a restricted cone type or a port restricted cone type, the fake packet opens a pinhole to the terminating NAT that will allow a response from the terminating NAT to penetrate the originating NAT. After sending the fake packet, the sequence 1500 proceeds with steps 1504, 1506, 1508, and 1510, which are similar to the reflection process described with respect to FIG. 12, and will not be described in detail in the present example. The endpoints 104 and 106 may then communicate directly, as indicated by step 1512.

Referring again to table 1100 of FIG. 11, if the originating NAT type is a symmetric type, then the originating NAT can establish communications with a terminating NAT type that is either no NAT or full cone after a port capture occurs. This process is described below with respect to FIG. 16.

Referring to FIG. 16, in step 1602, the endpoint 104 (symmetric NAT type) sends a message to the endpoint 106. In step 1604, the endpoint 106 captures the external port used by the NAT device 1004 in sending the message. This port, along with the address of the NAT device 1004, may then be used when communicating with the endpoint 104 directly, as indicated by step 1606.

Referring again to table 1100 of FIG. 11, if the originating NAT type is a restricted cone type, then the originating NAT can establish communications with a terminating NAT type that is symmetric by using a fake packet, reflecting a packet using the stateless reflector 1002, and then performing a port capture. This process is described below with respect to FIG. 17.

Referring to FIG. 17, in step 1702, the endpoint 104 sends a fake packet to the endpoint 106. Because the originating NAT type is a restricted cone type, the fake packet opens a pinhole to the terminating NAT that will allow a response from the terminating NAT to penetrate the originating NAT. After sending the fake packet, the sequence 1700 proceeds with steps 1704, 1706, 1708, and 1710, which are similar to the reflection process described with respect to FIG. 12, and will not be described in detail in the present example. In step 1712, the endpoint 104 captures the external port used by the NAT device 1006 in sending the acknowledgement in step 1710. This port, along with the address of the NAT device 1006, may then be used when communicating with the endpoint 106 directly, as indicated by step 1714.

Referring again to table 1100 of FIG. 11, if the originating NAT type is a symmetric type, then the originating NAT can establish communications with a terminating NAT type that is a restricted cone type by using a reflect, a fake packet, and a port capture. This process is described below with respect to FIG. 18.

Referring to FIG. 18, steps 1802, 1804, and 1806 are similar to the reflection process described with respect to FIG. 12, and will not be described in detail in the present example. In step 1808, in response to the reflected message from the endpoint 104, the endpoint 106 sends a fake packet to the endpoint 104. Because the terminating NAT type is a restricted cone type, the fake packet opens a pinhole to the endpoint 104 to allow messages from the endpoint 104 to traverse the NAT device 1006. Accordingly, in step 1810, the endpoint 104 can send the next message directly to the endpoint 106 through the pinhole. In step 1812, the endpoint 106 captures the external port used by the NAT device 1004 to send the message in step 1810. This port, along with the address of the NAT device 1004, may then be used by the endpoint 106 when communicating directly with the endpoint 104, as indicated by step 1814.

Referring again to table 1100 of FIG. 11, if the originating NAT type is a symmetric type and the terminating NAT type is a port restricted cone, or if the originating NAT type is a port restricted cone and the terminating NAT type is symmetric, then all signaling between the two NAT devices is relayed via the stateless reflector 1002, while media is transferred via peer-to-peer, as described previously. If both the originating and terminating NAT types are symmetric, then all signaling and media are relayed via the stateless reflector 1002.

Accordingly, the peer-to-peer communications described herein may be achieved regardless of the NAT type that may be used by an endpoint. The stateless reflector 1002 need not know the information for each client, but instead reflects various packets based on information contained within the packet that is to be reflected. Both the custom header and payload may be encrypted for security purposes. However, the stateless reflector 1002 may only be able to decrypt the custom header and the payload itself may only be decrypted by the terminating endpoint. This enables the stateless reflector 1002 to perform the reflection functionality while maintaining the security of the payload itself. As described above, not all processes for traversing a NAT device may use the stateless reflector 1002.

Referring to FIGS. 19A and 19B, in another embodiment, a peer-to-peer environment 1900 includes the two endpoints 104 and 106, the two NAT devices 1004 and 1006, and the stateless reflector 1002 of FIG. 10, and another endpoint 1901. Also illustrated are three possible routes between endpoints: a private (pr) route 1902, a public (pu) route 1904, and a reflected (rl) route 1906. FIG. 19A illustrates the routes 1902, 1904, and 1906 between the endpoint 104 and the endpoint 1901, and FIG. 19B illustrates the routes between the endpoint 104 and the endpoint 106. As will be discussed below in detail, the endpoints 104, 106, and 1901 may contain logic that allows one of the three routes 1902, 1904, and 1906 to be selected in a dynamic and flexible manner rather than relying on the rule-based system described above.

A rule-based system may be fairly inflexible, as such a system generally has a clear set of rules that are defined for various NAT situations and the current relationship between the two endpoints is handled according to those rules. Network configuration changes and other modifications may require revisions to the rules, which is not convenient and may prevent the endpoints from communicating until the rules are revised. Accordingly, in some embodiments, the flexibility described below may enable the endpoints 104, 106, and 1901 to adapt to new network configurations without requiring updated rules as would be required in a strictly rule-based system. In still other embodiments, the logic within the endpoints 104, 106, and 1901 may be updated to handle new network configurations, which also provides flexibility not found in strictly rule-based systems.

Each endpoint 104, 106, and 1901 may include one or more virtual interfaces for communication with other endpoints. In the present example, there are three virtual interfaces including a private virtual interface corresponding to the private route 1902, a public virtual interface corresponding to the public route 1904, and a relay virtual interface corresponding to the relay route 1906. It is understood that the term “virtual interface” is used only for purposes of description to clarify that there are multiple possible routes. Accordingly, the term “virtual interface” need not denote separate physical network interfaces on an endpoint, but may use a single physical network interface.

As described above, each endpoint 104, 106, and 1901 is generally associated with two IP address/port pairs. The first IP address/port pair may be the local (i.e., private) IP address/port information that represents each of the endpoints 104, 106, and 1901 in the network that is “inside” the corresponding NAT device 1004 or 1006. For example, the first IP address/port pair for the endpoint 104 may be the physical address assigned to the endpoint 104 by the corresponding NAT device 1004. This first IP address/port pair corresponds to the private virtual interface and may provide access via the private route to the endpoint 104 by endpoints in the same local network (e.g., the endpoint 1901). The second IP address/port pair may be the public IP address/port information that represents each of the endpoints 104, 106, and 1901 in the network that is “outside” the corresponding NAT device 1004 or 1006. For example, the second IP address/port pair for the endpoint 104 may be the address that is returned to the endpoint 104 by the STUN server as previously described (e.g., the NAT's external IP address/port pair assigned to the endpoint 104). This second IP address/port pair for the endpoint 104 corresponds to the public virtual interface and may provide access via the public route to the endpoint 104 by endpoints both inside and outside the endpoint 104′s local network. Each endpoint 104, 106, and 1901 is also aware of the address information of the reflector 1002 as described in previous embodiments, which corresponds to the relay virtual interface of the endpoints. The relay route may be used in (5,4), (4,5), and/or (5,5) conditions according to the table of FIG. 11, where one endpoint must send a packet first, but is unable to do so because the other endpoint must send a packet first.

Referring to FIG. 20, a sequence diagram illustrates one embodiment of a message sequence 2000 that may occur between the endpoints 104 and 1901 of FIG. 19A when identifying which of the routes (i.e., the private route 1902, the public route 1904, and the relay route 1906) will be used for communications. In the present example, the endpoints 104 and 1901 are in a local (i.e., private) network such as an Enterprise network, a local area network (LAN), a virtual LAN (VLAN), or a home network. This local network is isolated from the public network by the NAT device 1004 or a similar network component. Although shown as a single NAT device, it is understood that the NAT device 1004 may be a separate NAT device for each of the endpoints 104 and 1901. In contrast, the endpoint 106 is in a separate network that is only accessible by the endpoints 104 and 1901 via a public network that forms all or part of the packet network 108.

The present example uses a SIP messaging model over UDP, and so accommodates the transaction-based SIP model within connection-less UDP messaging. Because UDP is not transaction based, certain message handling processes may be used to conform to SIP standards, such as discarding multiple messages when the SIP model expects a message belonging to a specific transaction. However, it is understood that the sequence 2000 may be implemented using many different messaging models. In the present example, neither endpoint is online at the beginning of the sequence and the endpoints 104 and 1901 are “buddies.” As described above, buddies are endpoints that have both previously agreed to communicate with one another.

In steps 2002 and 2006, the endpoints 104 and 1901, respectively, send STUN requests to obtain their corresponding public IP address/port pairs (NATIP, NATPort). In the present example, the reflector 1002 is serving as a STUN server, but it is understood that the STUN server may be separate from the reflector. The reflector 1002 responds to the STUN requests with the public IP address and port information for each of the endpoints 104 and 1901 in steps 2004 and 2008, respectively.

As the two endpoints 104 and 1901 are not logged in when the present example begins, they must both authenticate with the access server 102. In step 2010, the endpoint 104 sends an authentication request to the access server 102 with its private and public IP address/port pairs. In step 2012, the access server 102 responds to the authentication request and, as described previously, returns information that includes the private and public IP addresses of any buddy endpoints that are currently logged in. However, as the endpoint 1901 has not yet logged in, the information received by the endpoint 104 from the access server 102 will not include any address information for the endpoint 1901.

In step 2014, the endpoint 1901 sends an authentication request to the access server 102 with its private and public IP address/port pairs. In step 2016, the access server 102 responds to the authentication request and, as described previously, returns information that includes the private and public IP addresses of any buddy endpoints that are currently logged in. As the endpoint 104 is currently logged in, the information received by the endpoint 1901 from the access server 102 will include the private and public address information for the endpoint 104. Although not shown, the endpoint 1901 may then send a message to the endpoint 104 informing the endpoint 104 that the endpoint 1901 is currently online. This message may contain the private and public address information of the endpoint 1901. The message may be sent via the three different routes as described below with respect to later messaging, or may be sent via one or more selected routes. For example, the message may only be relayed (i.e., sent via the relay route) due to the high chance of success of that route.

At this point, the endpoint 104 wants to establish a communication session with the endpoint 1901, but does not know which of the three routes (i.e., pr, pu, and rl) should be used. In the previously described rule-based system, the endpoint 1901 would publish its NAT information, which enables the endpoint 104 to determine how to establish a connection. However, in the present example, such information is not published and the endpoint 104 does not know whether the endpoint 1901 is in the same private network as the endpoint 104, whether the endpoint 1901 is only accessible via a public network, whether the endpoint 1901 is behind a NAT device, or, if the endpoint 1901 is behind a NAT device, the settings of the NAT device (full cone, port restricted, etc.). Accordingly, the endpoint 104 needs to dynamically determine which of the three routes to use with the endpoint 1901.

Accordingly, in step 2018, the endpoint 104 interacts with the endpoint 1901 to determine which of the three routes should be used to send messages to the endpoint 1901. Similarly, in step 2020, the endpoint 1901 interacts with the endpoint 104 to determine which of the three routes should be used to send messages to the endpoint 104, which may not be the same route as that used by the endpoint 104 to send messages to the endpoint 1901. Steps 2018 and 2020 are illustrated in greater detail below with respect to FIG. 21. In step 2022, the two endpoints communicate via the determined route(s).

Referring to FIG. 21, a sequence diagram illustrates one embodiment of a message sequence 2100 that may occur during steps 2018 and 2020 of FIG. 20 in order to determine which of the routes are to be used. The endpoint 104 may keep a table containing each buddy that is online and the route to be used for that buddy. For example, when the route is unknown, the table may have the information shown in Table 1 below:

TABLE 1 Buddy Endpoint Route (send-receive) 1901 unk-unk X X X X

The endpoint 104 (which is the originating endpoint in the present example) sends out three presence messages in steps 2102, 2104, and 2106. As the current example uses SIP messaging transported via UDP, the message is a SIP INFO message. More specifically, in step 2102, the endpoint 104 sends a SIP INFO message to the private IP address/port pair of the endpoint 1901 (i.e., via the private route) with an identifier such as a ‘pr’ tag to indicate the route. In step 2104, the endpoint 104 sends a SIP INFO message to the public (NAT) IP address/port pair of the endpoint 1901 (i.e., via the public route) with an identifier such as a ‘pu’ tag to indicate the route. In step 2106, the endpoint 104 sends a SIP INFO message to the endpoint 1901 via the reflector 1002 (i.e., via the relay route) with an identifier such as an ‘rl’ tag to indicate the route, which is reflected to the endpoint 1901 in step 2108.

The order in which the messages are sent may vary, but the order follows a hierarchy of desired routes in the present embodiment that places the private route first (i.e., most desirable), the public route next, and the relay route last (i.e., least desirable). However, it is understood that the order in which the messages are sent may vary or, if the endpoint 104 is capable of sending multiple messages simultaneously, the messages may be sent at the same time.

The present example assumes that the endpoint 1901 receives one or more of the messages sent in steps 2102, 2104, and 2106. If more than one message is received, the endpoint 1901 may respond only to the first one received. So, for example, if the message sent via the private route is received before the messages sent via the public and relay routes, the endpoint 1901 will respond only to the private route message and the later messages will be ignored. This reduces network traffic and provides for SIP compliance as the endpoint 104 (from a SIP perspective) expects to receive a single 200 OK message in response to its SIP INFO message. Furthermore, the response message may be sent back along the same route as the presence message to which the response is directed. So a response to the private route message will be sent back along the private route. Accordingly, only one of steps 2110A, 2110B, and 2110C-1 may occur in the present example. Step 2110C-2 is dependent on the occurrence of step 2110C-1 because the response message will not be reflected unless the relay route is used.

The response message returned by the endpoint 1901 is a SIP 200 OK message that may include the tag extracted from the received INFO message to identify which of the routes was successful (e.g., which route carried the message that was received first). For purposes of example, the private route was successful and the table may then be updated as shown in Table 2 below:

TABLE 2 Buddy Endpoint Route (send-receive) 1901 pr-unk X X X X

It is noted that since the private route is successful, the two endpoints 104 and 1901 are in the same private network.

It is understood that the response message (e.g., the SIP 200 OK) may never be received by the endpoint 104. For example, the private route may not be available from the endpoint 1901 to the endpoint 104 due to network configuration settings. Accordingly, if the SIP 200 OK is not received by the endpoint 104, the endpoint 104 may execute a retransmission process that resends the presence messages along the three routes. The resending may occur a set number of times, for a set period of time, or until some other limit is reached. For example, the first set of presence messages may be sent 0.5 seconds after the initial messages are sent, the second set of messages may be sent one second after that, and each additional set of messages may be sent at time periods that are double the previous delay until a total of seven sets of messages are sent. At this time, the endpoint 104 may stop sending messages. If a response is received during the retransmission process, the endpoint 104 will stop retransmitting. However, the response message will generally be received by the endpoint 104.

The outbound SIP INFO messages and the received SIP 200 OK message inform the endpoint 104 of which route to use when sending communications to the endpoint 1901. However, this route may not work in reverse. In other words, just because the endpoint 104 can reach the endpoint 1901 via the private route (to continue the example), it does not necessarily follow that the endpoint 1901 can reach the endpoint 104 using the same route. For example, differences in the configurations of NAT devices or other network differences may mean one endpoint can be reached via a particular route even if the reverse route is not available.

Accordingly, the endpoint 1901 sends out three presence messages in steps 2112, 2114, and 2116. As the current example uses SIP messaging transported via UDP, the message is a SIP INFO message. More specifically, in step 2112, the endpoint 1901 sends a SIP INFO message to the private IP address/port pair of the endpoint 104 (i.e., via the private route). In step 2114, the endpoint 1901 sends a SIP INFO message to the public (NAT) IP address/port pair of the endpoint 104 (i.e., via the public route). In step 2116, the endpoint 1901 sends a SIP INFO message to the endpoint 104 via the reflector 1002 (i.e., via the relay route), which is reflected to the endpoint 104 in step 2118.

The present example assumes that the endpoint 104 receives one or more of the messages sent in steps 2112, 2114, and 2116. If more than one message is received, the endpoint 104 may respond only to the first one received. Accordingly, only one of steps 2120A, 2120B, and 2120C-1 may occur in the present example. Step 2120C-2 is dependent on the occurrence of step 2120C-1 because the response message will not be reflected unless the relay route is used. The response message returned by the endpoint 104 is a SIP 200 OK message that identifies which of the routes was successful (e.g., was received first).

If the first (or only) SIP INFO message received by the endpoint 104 from the endpoint 1901 is received via the same route as that used by the endpoint 104 to send messages to the endpoint 1901 (e.g., the private route), then the communication session is established with messages going both ways on that route. At this point, the table may then be updated as shown in Table 3 below:

TABLE 3 Buddy Endpoint Route (send-receive) 1901 pr-pr X X X X

However, the first (or only) SIP INFO message received by the endpoint 104 from the endpoint 1901 may be received on a different route than that used by the endpoint 104 to send messages to the endpoint 1901. When this occurs, the endpoint 104 flags this as the endpoint 1901 responded to the INFO message via one route but is now communicating via another route. For example, the endpoint 1901 responded on the private route, but is now using the public route. One possibility for this discrepancy is that there is a router or other network device interfering with the return path (i.e., the path used by the endpoint 1901 to send messages to the endpoint 104). Another possibility is that a message went faster one way than another way. For example, while the endpoint 1901 may have received the private message from the endpoint 104 (i.e., the message of step 2102 of FIG. 21) before the other messages, the endpoint 104 may have received the public message from the endpoint 1901 (i.e., the message of step 2114 of FIG. 21) before the public and relay messages.

When this occurs, the endpoint 104 may transition from the private route to the public route. This results in sending and receiving routes of pu-pu as illustrated by Table 4 below:

TABLE 4 Buddy Endpoint Route (send-receive) 1901 pu-pu X X X X

The endpoint 104 may also be configured to confirm that this transition is correct. To confirm the transition, the endpoint 104 executes a confirmation process and sends a confirmation message to the endpoint 1901 on the private route (i.e., the route that the endpoint 104 thinks it should be using to send messages to the endpoint 1901). In the present example, the confirmation message may include a SIP field named MAX_FORWARDS that defines a maximum number of hops that a packet can take before being dropped. The MAX_FORWARDS field has a standard default value of seventy, but the endpoint 104 may set the value to one (i.e., MAX_FORWARDS=1). If the response message from the endpoint 1901 is received by the endpoint 104 and has set the MAX_FORWARDS field to 0, then the endpoint 104 transitions back to the private route and uses that route for sending future messages. This results in different sending and receiving routes as illustrated by Table 5 below:

TABLE 5 Buddy Endpoint Route (send-receive) 1901 pr-pu X X X X

However, if the endpoint 104 does not receive a response message to its confirmation message, it continues using the public route. This results in sending and receiving routes of pu-pu as illustrated by Table 4 above.

Communications between the endpoints 104 and 106 as illustrated in FIG. 19B may follow the same sequence of presence messages and responses as that described above with respect to FIGS. 20 and 21. However, since the endpoints 104 and 106 are in separate networks (i.e., not the same local network), the private route 1902 is not available and the private presence messages will fail to reach their destination. The presence messages may still be sent each way on the private route as the endpoints 104 and 106 do not know the location of the other endpoint, but the messages will be dropped. For example, the NAT devices 1004 and 1006 may both be routers that have an address of 192.168.1.1 in their respective home networks. The NAT device 1004 may assign a private address of 192.168.1.10 to the endpoint 104 and the NAT device 1006 may assign a private address of 192.168.1.15 to the endpoint 106. Although these addresses appear to be in the same local network, they are not. However, as the endpoints 104 and 106 have no way of knowing whether the private addresses are in the same local network until they perform their strategic routing sequences, they may both send their private presence messages along the private route, even though the messages will both fail. Accordingly, the endpoints 104 and 106 will use the public route 1904 and/or the relay route 1906 when communicating.

Referring to FIG. 22, a flowchart illustrates one embodiment of a method 2200 that may represent a process by which an endpoint such as the endpoint 104 of FIGS. 19A and 19B establishes a connection with another endpoint as described with respect to FIGS. 20 and 21 above.

In step 2202, the endpoint 104 sends outbound presence messages on the private, public, and relay routes. The presence messages may contain identifiers such as tags or other route indicators, or the receiving endpoint may simply note which virtual interface (i.e., pr, pu, or rl) received a particular presence message and correlate the message with the route upon receipt. In step 2204, the endpoint 104 receives a response message that indicates which of the presence messages was received first. For example, the response message may include the tag from the presence message to identify the route corresponding to the received presence message. In step 2206, the endpoint 104 selects the identified route as the initial outbound route for messages being sent to the other endpoint.

In step 2208, the endpoint receives one or more inbound presence messages from the other endpoint. In step 2210, the endpoint 104 sends a response to the first received inbound presence message.

In step 2212, the endpoint 104 determines whether the inbound route of the message received in step 2210 is the same route as the initial outbound route selected in step 2206. If the routes are the same, the method 2200 continues to step 2220 and uses the initial outbound route to send messages to the other endpoint. If the routes are not the same, the method 2200 moves to step 2214 and sends a confirmation message to the other endpoint using only the initial outbound route. In step 2216, the endpoint 104 determines whether a response to the confirmation message has been received. If no response to the confirmation message has been received, the method 2200 moves to step 2218 and transitions to the inbound route as the new outbound route for messages being sent to the other endpoint. If a response to the confirmation message has been received, the method 2200 continues to step 2220 and uses the initial outbound route to send messages to the other endpoint.

In step 2222, the endpoint 104 may begin sending keep-alive messages to the other endpoint to ensure that the outbound route remains open. For example, one of the networks or NAT devices involved in the established session may undergo a configuration change or a failure while the two endpoints are online, and so an existing route may become unusable. In such a case, the endpoint may detect that the keep-alive messages are failing and so may return to step 2202 to re-establish a valid route. It is noted that the other endpoint may not need to re-establish its outbound route. For example, if the inbound and outbound routes for the endpoint 104 are different, the inbound route may remain valid even though the outbound route is invalid. Accordingly, some steps of the method 2200 may be skipped in some scenarios.

It is noted that many different variations of the method 2200 may exist. For example, the endpoint 104 may transition to the inbound route as the new outbound route if it is determined in step 2212 that the routes are not the same, rather than remaining on the initial outbound route. Then, if a response is received to the confirmation message, the endpoint 104 may transition back to the initial outbound virtual interface. Furthermore, as stated previously, the response message may never be received by the endpoint 104 and so some steps of the method 2200 may not occur or may occur in a different order as there may be no response message available to determine the initial outbound route. It is also noted that some steps of the method 2200 may be performed in a different order than shown. For example, step 2208 may occur before step 2204 depending on network latency and other factors.

Referring to FIGS. 23A and 23B, in another embodiment, the endpoints 104 and 106, the two NAT devices 1004 and 1006, and the stateless reflector 1002 of FIGS. 19A and 19B are illustrated with a tunneling server or other access device 2302 and another endpoint 2304. The tunneling server 2402 may provide access to other endpoints for an endpoint that does not have UDP access or access to another expected protocol. For example, if the endpoint 104 performs a STUN request and the request fails, the network within which the endpoint 104 is positioned may not support UDP (e.g., the network may be an Enterprise network that has disabled UDP). For purposes of illustration, the endpoints 104 and 2304 are in a private network and not separated by the NAT device 1004, and the endpoint 106 is separated from the endpoint 104 by the NAT devices 1004 and 1006.

Referring to FIG. 24, a sequence diagram illustrates one embodiment of a message sequence 2400 that may occur in the environment of FIGS. 23A and 23B to establish a connection between the endpoints 104 and 106. As with the previous discussion of FIG. 20, the endpoints 104 and 106 may each maintain a table, although this is not shown in the present example.

In step 2402, the endpoint 104 sends a STUN request that fails. Based on the failure of the STUN request, the endpoint 104 determines that the network (e.g., the NAT device 1004) has disabled UDP. It is understood that other indicators may be used to determine that UDP is not available. In step 2404, based on the unavailability of UDP, the endpoint 104 opens a TCP/IP connection (i.e., a tunnel) with the tunneling server 2302. This connection may use a port such as port 443 of the NAT device 1004, which is the default TCP port for HTTP Secure (HTTPS) connections using the Transport Layer Security (TLS) or Secure Socket Layer (SSL) protocols. However, it is understood that port 443 is only an example and that other available ports may be used. In step 2406, the endpoint 104 requests a shadow IP address and shadow port on the tunneling server 2302. In step 2408, the tunneling server 2302 creates the shadow IP address and port and returns this information to the endpoint 104 in step 2410.

The shadow IP address and shadow port serve as the public address and port of the endpoint 104 for other endpoints. In other words, the shadow IP address/port replace the NAT IP address/port that would serve as the public contact information for the endpoint 104 in an environment in which UDP is available to the endpoint 104 (e.g., as in FIGS. 19A and 19B). In some embodiments, the shadow IP address/port pairs may be placed on a shadow list as they are provisioned and the shadow list may be available to the access server 102 and/or endpoints. In other embodiments, the access server 102 and/or endpoints may have a list or range of IP addresses/ports that are known to be shadows. In still other embodiments, the knowledge of whether an IP address/port is a shadow is not available to the access server 102 and/or endpoints.

In step 2412, the endpoint 104 authenticates with the access server 102 via the tunnel using its local IP address/port and shadow address/port information. In step 2414, the access server 102 authenticates the endpoint 104 and sends the endpoint 104 the contact information of online buddies, including corresponding private, public, and shadow IP address/port information.

Although not shown in FIG. 24, the endpoint 106 sends a request to a STUN server and receives its public IP address/port information as described with respect to the endpoints 104 and 1901 in FIG. 20. Since the endpoint 106 is successful with its STUN request, it does not need to use the tunneling server 2302. In steps 2416 and 2418, the endpoint 106 authenticates with the access server and receives the private IP address/port and shadow IP address/port of the endpoint 104. As discussed above, the endpoint 106 may or may not know that the endpoint 104 is using a shadow, depending on the particular implementation of the shadow list.

In steps 2420 and 2422, the endpoints 104 and 106 may establish a communication session as described previously with respect to FIGS. 20 and 21. However, the communications between the two endpoints 104 and 106 will use the tunnel between the endpoint 104 and the tunneling server 2302 and the corresponding shadow IP address and port for the endpoint 104.

In embodiments where the endpoint 106 knows that the endpoint 104 is using a shadow, the endpoint 106 may not send a presence message via the private route as the endpoint 106 knows that the private route is not available. In other embodiments, the endpoint 106 may send a presence message via the private route even though the route is not available.

Communications between the endpoints 104 and 2304 as illustrated in FIG. 23B may follow a similar sequence of presence messages and responses as that described above with respect to FIG. 24. However, since the endpoints 104 and 2304 are in the same local network, the private route 1902 is available and the private presence messages may reach their destinations. The endpoint 2304 may not use a relay message to try to reach the endpoint 104, since its failed STUN request will inform the endpoint 2304 that UDP is not available. In order to use the public and relay routes, the endpoint 2304 will create a tunnel with the tunneling server 2303 as described above with respect to the endpoint 104. The public and relay messages may still work via the respective tunnels of the endpoints 104 and 2304.

Referring to FIG. 25, in another embodiment, an environment 2500 is illustrated in which an endpoint (e.g., the endpoint 104 of FIG. 1) may communicate with a device 2502 that is not an endpoint. For example, the device 2502 may not contain the endpoint engine 252 described with respect to FIG. 2 b and may be unable to login to a peer-to-peer network associated with the access server 102 (FIG. 1) and/or may be unable to communicate directly with the endpoint 104 due to the lack of required endpoint functionality. In some embodiments, the device 2502 may be in a restricted environment, in which case it may not be possible to provide the endpoint engine 252 to the device due to the restrictions. For example, the device 2502 may be a television set-top box and such boxes are generally restricted environments that are closed to applications such as are needed for endpoint functionality. In other embodiments, the device 2502 may not be capable of supporting the endpoint engine 252. For example, the device 2502 may lack sufficient memory and/or processing power for the endpoint engine 252 and/or may not have a suitable communications link. For example, the device 2502 may be a television that is not capable of providing the needed environment for the endpoint engine 252.

In the present example, a third party system 2504 handles communications to and from the device 2502. The third party system 2504 may be any type of system and need not be ordinarily configured for communications with a device such as the endpoint 104. For example, the device 2502 may be a television or a television set-top box, a tablet such as those commonly used by delivery services, a cellular telephone, or any other device capable of interacting with a user to receive input data from the user and/or send output data to the user. The device 2502 may also represent a combination of other devices, such as a television and television set-top box combination, with the television providing display and audio output for the set-top box and input occurring via a remote control or other input device. It is understood that if the device 2502 does not have an output component (e.g., a screen and/or speaker) and/or some type of input device, then the third party system 2504 may provide such functionality to the device.

The third party system 2504 may be a “black box” from the perspective of the peer-to-peer network components such as the endpoint 104 and the access server 102. However, although the third party system 2504 may be a black box in terms of its internal operation, it may provide an Application Programming Interface (API) that enables an exterior system to communicate with the third party system. In some embodiments, the third party system 2504 may be a proprietary system, in which case the API may be provided by an operator of the third party system 2504.

As is described below in greater detail, the API of the third party system 2504 enables external systems and devices (e.g., the endpoint 104) to communicate with the third party system 2504 and devices internal to the third party system, such as the device 2502. Because the API is known, communications between the endpoint 104 and the device 2502 may be converted (i.e., reformatted) as needed. The third party system 2504 and/or components within the peer-to-peer network may handle such conversions. This allows the device 2502 to behave as an endpoint without actually having the endpoint functionality that is on an endpoint such as the endpoint 104.

To facilitate communications between the endpoint 104 and the device 2502, a peer-to-peer shadow server 2506 is provided. Although the shadow server 2506 may be configured in many different ways, in the present example the shadow server 2506 may include a virtualized endpoint management module (VEMM) 2508. The VEMM 2508 may maintain a list of “mapped endpoints” that represent devices that are not themselves endpoints, such as the device 2502. The mapped endpoints may be controlled in many different ways. For example, the mapped endpoints may only include devices that are registered with the VEMM 2508. In another example, the mapped devices may be any devices that are accessible via the third party system 2504. In still another example, the mapped devices may be any devices that are accessible via the third party system 2504 that meet certain criteria (e.g., have defined input and output capabilities or are subscribers of a service).

Each of the mapped endpoints represents a device that is able to interact with a “real endpoint” (e.g., the endpoint 104 that contains the needed functionality to perform as an endpoint, such as the endpoint engine 252) via the VEMM 2508. For each of the mapped endpoints, the VEMM 2508 provides a “virtual endpoint” that represents the mapped endpoint in the peer-to-peer network. Accordingly, in the present example, the device 2502 is a mapped endpoint 2510 that is represented by a virtual endpoint 2512. It is understood that, in the present embodiment, the device 2502 may exist without a corresponding mapped endpoint 2510, but the mapped endpoint may not exist without the device 2502. As the device 2502 may be one of many different devices or combinations of devices as described above, it will frequently be referred to as the mapped endpoint 2510 in the following examples. From an operational perspective, the VEMM 2508 may deal with the mapped endpoint 2510, rather than with the device 2502.

The shadow server 2506 may be coupled to other components of a peer-to-peer environment, such as the access server 102 of FIG. 1, a reflector/STUN server such as the reflector 1002 of FIG. 10, and a tunneling server such as the tunneling server 2302 of FIG. 23. As these are described in detail above and/or in the text as incorporated by reference, they are not described further in the present example. It is understood that the shadow server 2506 has access to servers just as the endpoint 104 has access to such servers, and the shadow server 2506 may use these servers when needed (e.g., to authenticate a user or to perform NAT traversal functions).

In the present example, the shadow server 2506 (e.g., via the VEMM 2508) is coupled to the third party system 2504 via a signaling/media interface 2514 that provides a head-end signaling interface 2516 for handling signaling and a media transfer interface 2518 for handling media (e.g., video, audio, and/or data). Although shown as a separate component of the environment 2500, the signaling/media interface 2514 may be part of the shadow server 2506 or part of the third party system 2504. It is understood that the signaling/media interface 2514 may not be configured as shown, but provides the functionality needed to handle the signaling and media traffic of an endpoint as described previously.

In some embodiments, the media/signaling interface 2514 may not be needed and may be bypassed for some or all communications. In this case, the following embodiments may be similar except that the media/signaling interface 2514 may be removed. In still other embodiments, the VEMM 2508 may only instantiate the virtual endpoint 2512 and may not be part of the communications after the instantiation is complete. In this case, the following embodiments may be similar except that the VEMM 2508 may be removed except for virtual endpoint instantiation.

The VEMM 2508 may handle virtual client instantiation and management and may also handle traffic to and from the mapped endpoint 2510. In some embodiments, all signaling and media traffic may pass through the VEMM 2508 to and from the signaling/media interface 2514, while in other embodiments one or both of the signaling and media traffic may pass directly between the virtual endpoint 2512 and the signaling/media interface 2514 without passing through the VEMM 2508. For example, signaling traffic between the virtual endpoint 2512 and the signaling/media interface 2514 may pass through the VEMM 2508, while media traffic may bypass the VEMM 2508 and go directly between the virtual endpoint 2512 and the signaling/media interface 2514.

In the following examples, the peer-to-peer network may be based on a SIP messaging model over UDP while the third party system 2504 may use an entirely different proprietary or non-proprietary protocol or set of protocols that is incompatible with the SIP/UDP model. For example, if the device 2502 is a television and is responsive only to satellite or cable television signals provided by the third party system 2504, then the device 2502 is not compatible with messaging using the SIP/UDP model. Accordingly, the signaling/media interface or another component of the peer-to-peer network and/or the third party system 2504 may handle the conversions and formatting needed in order for the peer-to-peer network and the third party system 2504 to communicate despite the differing protocols.

Although single components of the peer-to-peer network are illustrated in FIG. 25, it is understood that multiple components may be used. For example, multiple shadow servers may be used for load balancing and/or other purposes and so the present disclosure is not limited to the configuration shown.

Referring to FIG. 26, a sequence diagram illustrates one embodiment of a message sequence 2600 that may occur in the environment 2500 of FIG. 25 when the device 2502 logs into the peer-to-peer network. In the present example, the endpoint 104 is a buddy to the mapped endpoint 2510 and/or the virtual endpoint 2512 and so each has already authorized communications from the other buddy as described in previous embodiments. Furthermore, the endpoint 104 has already logged into the peer-to-peer network and is online prior to the initial step of the message sequence 2600 or at least prior to step 2626. It is understood that all of the communications between the VEMM 2508 and the mapped endpoint 2510 may go through the third party system 2504, although the third party system is not explicitly shown in FIG. 26. Accordingly, the communications may be converted or otherwise manipulated as needed in order to provide output to and to receive input from the device 2502.

In step 2602, the mapped endpoint 2510 sends a login request to the signaling interface 2516. In step 2604, the signaling interface 2516 passes the request to the VEMM 2508. The signaling interface 2516 may simply pass the request on to the VEMM 2508 or may reformat the request as needed. It is understood that, in some embodiments, the mapped endpoint 2510 may not actually be mapped until the request is received by the VEMM 2508. For example, the device 2502 may send the request and, when the request is received by the VEMM 2508, the VEMM 2508 may then map the device 2502. Alternatively, the mapping may exist prior to the request and the VEMM 2508 may view the request as being received from the mapped endpoint 2510.

In step 2606, the VEMM 2508 determines whether a virtual endpoint already exists for the mapped endpoint 2510. For example, the mapped endpoint 2510 may have lost communication and may log in after restoring communication. If the virtual endpoint has remained alive during this time, the VEMM 2508 may associate the current login request with the existing virtual endpoint and not create a new endpoint. If no virtual endpoint exists as determined in step 2606, the VEMM 2508 creates the virtual endpoint 2512 (assuming sufficient memory and other technical requirements are met) in step 2608 and receives confirmation of its creation in step 2610. In the present example, the virtual endpoint 2512 is an instanced endpoint that exists in the memory of the server 2506 once instantiated by the VEMM 2508.

The virtual endpoint 2512 may return a value or other indicator to the VEMM 2508 indicating that it was successfully instantiated and is ready for use. If the instantiation fails, a message may be returned to the device 2502 that the virtual endpoint cannot be created. This message may indicate simply that the login failed or may provide more detailed information. The instance may be destroyed when the mapped endpoint 2510 logs off or may be maintained based on settings of the VEMM 2508. In the present example, the virtual endpoint 2512 has the same capabilities as a real endpoint and so may perform the same functions as the endpoints described in previous embodiments. It is understood, however, that in some embodiments the functionality of the virtual endpoint 2512 may be limited by configuration or security settings of the shadow server 2502 and/or the third party system 2510.

In steps 2612 and 2614, the VEMM 2508 may send a message to the mapped endpoint 2510 to display a login screen. For example, the message from the VEMM 2508 may notify the third party system 2504 that it needs to provide a particular display to the mapped endpoint 2510. The third party system 2504 may then provide the needed display. This may happen in environments where the device 2502 is a device such as a television, where the login window may be a video overlay that appears on the television screen. The instructions may prompt the cable or satellite operator to provide the video overlay using the cable or television equipment coupled to the television and controlled by the operator. In other embodiments, the VEMM 2508 may send instructions to the mapped endpoint 2510 instructing the mapped endpoint to display the login screen. Accordingly, the actual display process and the particular instructions may depend on the implementation of the device 2502 and the third party system 2504.

In steps 2616 and 2618, the mapped endpoint 2510 provides login information (e.g., user name and authentication information as previously described) to the VEMM 2508. In step 2620, the VEMM 2508 provides the login information to the virtual endpoint 2512.

In step 2622, the virtual endpoint 2512 contacts the reflector 1002 and requests the public IP address and port information of the virtual endpoint. The process of obtaining this information and possible uses for this information are described in previous embodiments and are not described in detail in the present example. It is noted that step 2622 may occur without input from mapped endpoint 2510, as this step may rely on endpoint functionality of which the mapped endpoint 2510 is unaware. In step 2624, the virtual endpoint 2512 receives the public IP address and port information from the reflector 1002.

In step 2626, the virtual endpoint 2512 logs into the access server 102 by providing its username, password, local (NAT) IP address and port information, and public IP address and port information to the access server. If the authentication fails, a message may be sent by the virtual endpoint 2512 to the mapped endpoint 2510 indicating that the login has failed. In step 2628, the access server 102 sends the buddy list associated with the login information to the virtual endpoint 2512 as described previously. In step 2630, the virtual endpoint 2512 sends the buddy list to the VEMM 2508.

In steps 2632 and 2634, the VEMM 2508 sends a message to the mapped endpoint 2510 via the signaling interface 2516 to display the buddy list. For example, the message from the VEMM 2508 may be used by the third party system 2504 to display the buddy list based on user interface elements provided or controlled by the third party system or the mapped endpoint 2510.

In step 2636, the virtual endpoint 2512 sends a presence message to the endpoint 104 to inform the endpoint 104 that the mapped endpoint 2510 is online. In the present example, the message is a SIP presence message and, in step 2638, the endpoint 104 responds with a 200 OK to the virtual endpoint 2512. Although SIP is used for purposes of example, it is understood that many different types of messaging may be used and the presence message and reply may not be SIP messages. In step 2640, the virtual endpoint 2512 informs the VEMM 2508 that the endpoint 104 is online and, in steps 2642 and 2644, the VEMM 2508 sends a message to the mapped endpoint 2510 via the signaling interface 2516 to indicate that the endpoint 104 is online. In some embodiments, steps 2638, 2640, 2642, and 2644 may not occur as the endpoint 104 is online prior to the login of the mapped endpoint 2510 and will be in the buddy list with an online status when the buddy list is returned to the mapped endpoint.

Referring to FIG. 27, a sequence diagram illustrates one embodiment of a message sequence 2700 that may occur in the environment 2500 of FIG. 25 after the mapped endpoint 2510 is logged into the peer-to-peer network via the virtual endpoint 2512. In the present example, the mapped endpoint 2510 and the endpoint 104 are buddies and have already approved communications as described in previous embodiments. In the present example, the mapped endpoint 2510 is to place an audio call to the endpoint 104.

In steps 2702 and 2704, the mapped endpoint 2510 sends a message to the VEMM 2508 via the signaling interface 2516 to place the call. In step 2706, the VEMM 2508 forwards the message (with or without additional formatting) to the virtual endpoint 2512. In step 2708, the virtual endpoint 2512 places the call by sending a message to the endpoint 104. In the present example, the message is a SIP INVITE message. In step 2710, the endpoint 104 responds to the virtual endpoint 2512 with a 200 OK message (or another type of response message depending on the messaging type used) to accept the call. If the call were to be rejected by the endpoint 104, the following steps would denote rejection rather than acceptance.

In step 2712, the virtual endpoint 2512 sends a message to the VEMM 2508 notifying the VEMM that the call has been accepted by the endpoint 104. The message sent by the virtual endpoint 2512 may be the 200 OK message itself or may be another message. In steps 2714 and 2716, the VEMM 2508 sends a message to the mapped endpoint 2510 via the signaling interface 2516 that the call has been accepted and this is displayed on a user interface of the mapped endpoint.

In the present example, the call may then proceed with audio encapsulated data passing between the mapped endpoint 2510 and the media interface 2518 as shown by arrow 2718, audio encapsulated packets passing between the media interface 2518 and the virtual endpoint 2512 as shown by arrow 2720, and data based on the real-time transport protocol (RTP) or another suitable protocol passing between the virtual endpoint 2512 and the endpoint 104 as shown by arrow 2722. In some embodiments, the audio encapsulated data may be in packet format depending on the messaging system used by the third party system 2504 and the device 2502. For example, if the device 2502 is a television and the third party system 2504 is a cable television company, the messaging type for arrow 2518 would be compatible with cable television and may include overlays generated by a set-top box or other controller for display on the television. If the device 2502 is a cellular telephone (e.g., a phone based on a network protocol such as the Global System for Mobile Communications (GSM) or Code Division Multiple Access (CDMA)) or another device that uses a cellular network and the third party system 2504 is a cellular telephone provider, the messaging type would be compatible with the network type and the particular device.

Referring to FIG. 28, a sequence diagram illustrates one embodiment of a message sequence 2800 that may occur in the environment of FIG. 25 after the mapped endpoint 2510 is logged into the peer-to-peer network. In the present example, the mapped endpoint 2510 and the endpoint 104 are buddies and have already approved communications as described in previous embodiments. In the present example, the mapped endpoint 2510 is to receive an audio call placed by the endpoint 104.

In step 2802, the endpoint 104 sends a SIP invite message (or other message depending on the messaging type being used) to the virtual endpoint 2512. In step 2804, the virtual endpoint 2512 sends the call request to the VEMM 2508. The call request may be the SIP message itself or may be another message indicating that a call request has been received from the endpoint 104. In steps 2806 and 2808, the call request is forwarded to the mapped endpoint 2510.

In step 2810, the mapped endpoint 2510 responds to the call request by rejecting or accepting the call. In the present example, the request is accepted and the acceptance is passed to the virtual endpoint 2512 via the signaling interface 2516 and VEMM 2508 in steps 2810, 2812, and 2814. In step 2816, the virtual endpoint 2512 sends a 200 OK message to the endpoint 104 indicating that the mapped endpoint 2510 has accepted the call.

In the present example, the call may then proceed with audio encapsulated data passing between the mapped endpoint 2510 and the media interface 2518 as shown by arrow 2818, audio encapsulated packets passing between the media interface 2518 and the virtual endpoint 2512 as shown by arrow 2820, and data based on RTP or another suitable protocol passing between the virtual endpoint 2512 and the endpoint 104 as shown by arrow 2822.

Referring again to FIG. 25, in another embodiment, three devices 2502, 2520, and 2522 correspond to mapped endpoints 2510, 2524, and 2526, respectively. The mapped endpoints are associated with virtual endpoints 2512, 2528, and 2530, respectively. As illustrated in FIG. 25, the mapped endpoints 2524 and 2526 may communicate with one another via their respective virtual endpoints 2528 and 2530. This enables the devices 2520 and 2522, which are not real endpoints, to communicate via the peer-to-peer network in a manner similar to that of the device 2502. The connection between the virtual endpoints 2528 and 2530 may route out of and back into the shadow server 2506 as illustrated by line 2532 or may occur internally as illustrated by line 2534. It is understood that generally only one of lines 2532 or 2534 would exist. In the environment 2500 of FIG. 25, the virtual endpoint 2528 is also coupled to the endpoint 104. For example, the virtual endpoint 2528 may be anchoring a conference call with the virtual endpoint 2530 and the endpoint 104. Accordingly, a virtual endpoint may behave like a real endpoint and have many different connections to other virtual and real endpoints.

Referring to FIG. 29, a sequence diagram illustrates one embodiment of a message sequence 2900 that may occur in the environment of FIG. 25 after the mapped endpoints 2524 and 2526 are logged into the peer-to-peer network. In the present example, the mapped endpoints 2524 and 2526 are buddies and have already approved communications as described in previous embodiments. In the present example, the mapped endpoint 2524 is to place a call to the mapped endpoint 2526.

In steps 2902 and 2904, the mapped endpoint 2524 sends a message to the VEMM 2508 via the signaling interface 2516 to place the call. In step 2906, the VEMM 2508 forwards the message (with or without additional formatting) to the virtual endpoint 2528. In step 2908, the virtual endpoint 2528 places the call by sending a message to the virtual endpoint 2530. In the present example, the message is a SIP INVITE message.

In step 2910, the virtual endpoint 2530 sends the call request to the VEMM 2508. The call request may be the SIP message itself or may be another message indicating that a call request has been received from the virtual endpoint 2528. In steps 2912 and 2914, the call request is forwarded to the mapped endpoint 2526.

In step 2910, the mapped endpoint 2526 responds to the call request by rejecting or accepting the call. In the present example, the request is accepted and the acceptance is passed to the virtual endpoint 2530 via the signaling interface 2516 and VEMM 2508 in steps 2916, 2918, and 2920. In step 2922, the virtual endpoint 2530 sends a 200 OK message to the virtual endpoint 2528 indicating that the mapped endpoint 2526 has accepted the call.

In step 2924, the virtual endpoint 2528 sends a message to the VEMM 2508 notifying the VEMM that the call has been accepted by the virtual endpoint 2530. The message sent by the virtual endpoint 2528 may be the 200 OK message itself or may be another message. In steps 2926 and 2928, the VEMM 2508 sends a message to the mapped endpoint 2524 via the signaling interface 2516 that the call has been accepted and this is displayed on a user interface of the mapped endpoint.

In the present example, the call may then proceed with audio encapsulated data passing between the mapped endpoint 2524 and the media interface 2518 as shown by arrow 2930 and audio encapsulated packets passing between the media interface 2518 and the virtual endpoint 2528 as shown by arrow 2932. Similarly, audio encapsulated data passes between the mapped endpoint 2526 and the media interface 2518 as shown by arrow 2934 and audio encapsulated packets pass between the media interface 2518 and the virtual endpoint 2530 as shown by arrow 2936. Data based on RTP or another suitable protocol passes between the virtual endpoint 2528 and the virtual endpoint 2530 as shown by arrow 2938.

Although not shown in FIG. 29, the virtual endpoint 2528 may add the endpoint 104 to the call as described with respect to FIG. 27. This enables the virtual endpoint 2528 to establish a conference call with both virtual and/or real endpoints.

Accordingly, described above are embodiments illustrating how one or more virtual endpoints can be provided in a peer-to-peer network so that devices that are not themselves endpoints can communicate as peers within the network. Each virtual endpoint may have the same capabilities as a real endpoint and so may perform the same functions described in previous embodiments. Examples of such endpoint functions are described herein and in previously incorporated U.S. Pat. No. 7,570,636 and U.S. patent application Ser. No. 12/705,925. A mapped endpoint may send messages to the virtual endpoint that are to be passed to other endpoints, but the virtual endpoint generally handles all endpoint functionality. In such embodiments, the mapped endpoint may be viewed as a “dumb terminal” from the perspective of the peer-to-peer network that provides a user interface but provides no actual endpoint functionality.

Referring to FIG. 30, in another embodiment, an environment 3000 is illustrated in which an endpoint (e.g., the endpoint 104 of FIG. 1) may establish a communication session with another endpoint (e.g., the endpoint 106 of FIG. 1) using a reverse invitation. As will be described in greater detail below, the reverse invitation (represented by arrow 3008) may enable the endpoint 106 to switch an incoming call (represented by arrow 3006) from a first network, such as a PSTN or cellular network, to a second network, such as an IP network (e.g., WiFi), before the call is established on the first network.

In the present example, each endpoint 104 and 106 is a mobile handset associated with a telephone number as defined in the E.164 ITU-T recommendation used in networks such as the PSTN. For example, the endpoint 104 may be associated with the telephone number 214-555-1212 and the endpoint 106 may be associated with the telephone number 972-555-1212. Each endpoint 104 and 106 may be accessed by other devices when its associated number is dialed. Each endpoint 104 and 106 is also associated with a unique Electronic Serial Number (ESN) or an International Mobile Equipment Identity (IMEI) number.

It is understood that the endpoints 104 and 106 represent many different devices and that mobile handsets are used for purposes of illustration only. For example, an endpoint may be personal computing device with a modem card having an RJ-11 connection that can receive phone calls via TDM or a wireless card for cellular or Wi-Fi based calls. In such embodiments, the device may be capable of handling two communications (e.g., an IP session and a PSTN call) on the same line. It is understood that many different configurations are possible for a personal computing device, such as having an RJ-11 and an RJ-45 connection, access via a wireless router, having a 3G card, etc. An endpoint may also be a laptop, a PDA, or any other device capable of executing the endpoint functionality described herein.

Each endpoint 104 and 106 includes a background process 3002 and 3004, respectively, that runs on the device hosting the endpoint. The background processes 3002 and 3004 provide certain functions that enable each respective endpoint 104 and 106 to function as an endpoint within a hybrid peer-to-peer network. For example, when the background process 3002 launches, the background process 3002 may determine whether the corresponding endpoint 104 has connectivity to a data network, such as a WiFi network, a 3G or 4G data network, or any other data network that enables the endpoint 104 to send and receive data. The background process 3002 may also perform previously described functions such as authentication and presence notification.

In the present example, if the access server 102 (FIG. 1) does not already have the E.164 number and the ESN/IMEI number of the endpoint 104, the background process 3002 may also register the E.164 number and the ESN/IMEI number with the access server 102. The access server 102 may then store the information in the profile or elsewhere and may provide the information to other endpoints. For example, if the endpoint 106 logs on after the endpoint 104, the endpoint 106 may receive the E.164 number and the ESN/IMEI number of the endpoint 104 following the authentication process.

It is understood that one or both of the background processes 3002 and 3004 may be executed by their respective endpoints 104 and 106 at different privilege levels and/or using different configurations that may in turn determine whether the background process runs automatically or must be launched by a user. For example, in the mobile handset containing the endpoint 104, the background process 3002 may run automatically when the handset is turned on or may require that the user select and launch the background process 3002 as an application.

Referring to FIG. 31, a sequence diagram illustrates one embodiment of a message sequence 3100 that may occur in the environment 3000 of FIG. 30. Steps 3102, 3104, 3106, and 3108 are similar or identical to steps described in previous embodiments (e.g., steps 402, 404, 406, and 408 of FIG. 4) and are not described in detail in the present example. It is noted that registration of the E.164 number and the ESN/IMEI number of an endpoint may occur during this time and that the received profile may include the E.164 number and the ESN/IMEI number of buddy endpoints identified in the profile. In the present example, the endpoints 104 and 106 are buddies and both endpoints are online (e.g., have a visible presence to buddy endpoints).

In step 3110, the endpoint 104 receives a series of digits (e.g., 9725551212) representing an E.164 number. The endpoint 104 identifies the E.164 number as corresponding to the endpoint 106 and, in step 3112, the endpoint 104 initiates the call to the endpoint 106 by dialing the E.164 number of the endpoint 106. Although the call may be initiated by the endpoint 104 using many different call and/or network types (e.g., PSTN, cellular such as GSM or CDMA, or VoIP), the call is a cellular call for purposes of illustration. In step 3114, the endpoint 106 determines whether to switch to an IP network for the call instead of remaining on the network type used for the incoming call. For example, the endpoint 106 may determine whether an IP network is available or, if available, is suitable to support the call rather than remain on the cellular network through which the endpoint 104 is making the call.

In the present example, the endpoint 106 determines that the call should be switched to the IP network and, in step 3116, sends an invitation message to the endpoint 104. The invitation message is a request from the endpoint 106 to the endpoint 104 to establish an IP communication session. In step 3118, the endpoint 106 accepts the request. For purposes of example, the request includes a SIP INVITE message and the response includes a 200 OK message. The request may be auto-accepted by the endpoint 104 or may require acceptance by a user of the endpoint 104. In step 3120, assuming the request was accepted, the endpoints 104 and 106 establish the IP communication session. The establishment of the IP communication session may occur as described in previous embodiments. For example, the endpoints 104 and 106 may determine whether to use one or more private, public, or relay routes.

In steps 3122 and 3124, the non-IP leg of the call that was initiated by the endpoint 104 in step 3112 is torn down by the endpoints 106 and 104, respectively. It is understood that the call tear down may occur prior to or during the establishment of the IP communication session in step 3120 and that the order of steps 3122 and 3124 may be reversed or may occur simultaneously.

Accordingly, the original cell call initiated by the endpoint 104 in step 3112 may be transitioned to the IP communication session established in step 3120. This process may occur seamlessly to the users. For example, the user of the endpoint 104 dials the desired E.164 number. The user of the endpoint 106 does not need to establish a new call via an IP network, but may set preferences to configure the behavior of the endpoint 106 to automatically attempt to establish an IP call. The incoming E.164 may be put on hold, allowed to ring, or otherwise handled by the endpoint 106 while the endpoint 106 attempts to establish the IP communication session.

Referring to FIG. 32, a sequence diagram illustrates one embodiment of a message sequence 3200 that may occur in the environment 3000 of FIG. 30. Steps 3202, 3204, 3206, and 3208 are similar or identical to steps described in previous embodiments (e.g., steps 402, 404, 406, and 408 of FIG. 4) and are not described in detail in the present example. It is noted that registration of the E.164 number and the ESN/IMEI number of an endpoint may occur during this time and that the received profile may include the E.164 number and the ESN/IMEI number of buddy endpoints identified in the profile. In the present example, the endpoints 104 and 106 are buddies and both endpoints are online (e.g., have a visible presence to buddy endpoints).

In step 3210, the endpoint 104 initiates a call to the endpoint 106 by dialing the E.164 number of the endpoint 106. Although the call may be initiated by the endpoint 104 using many different call and/or network types (e.g., PSTN, cellular, VoIP), the call is a cellular call for purposes of illustration. In step 3212, the endpoint 106 determines whether to switch to an IP network for the call. For example, the endpoint 106 may determine whether an IP network is available or, if available, is suitable to support the call. In the present example, the endpoint 106 does not switch the call to the IP network and, in step 3214, answers the call and continues the call as initiated by the endpoint 104.

It is noted that, from the perspective of the endpoint 104, the sequence 3200 may remain unchanged if the endpoint 106 is not online or is not even an endpoint (e.g., is a device such as a conventional telephone without endpoint capabilities or is a device that is capable of being an endpoint but is not configured as such). For example, if the endpoint 106 is a regular telephone rather than an endpoint, the message sequence from the perspective of the endpoint 104 may not change as it may still call the telephone and wait for a response. Similarly, from the perspective of the endpoint 106, the sequence 3200 may be the same if the endpoint 104 is not online or is not an endpoint. In such embodiments, step 3212 may include a decision to not establish an IP communication session as the endpoint 106 would not see an available endpoint with which to establish the IP communication session.

Referring to FIG. 33, a flowchart illustrates one embodiment of a method 3300 that may represent a process by which an endpoint such as the endpoint 104 of FIG. 30 establishes a connection with the endpoint 106 as described with respect to FIG. 31 above. At the beginning of the method 3300, the endpoint 104 is active and has logged into a peer-to-peer network as previously described.

In step 3302, the endpoint 104 receives a plurality of digits as input. Additional input, such as a call or talk indicator, may also be received to initiate a call. Accordingly, in step 3304, the endpoint 106 initiates a call to the destination identified by the digits. It is understood that the destination may be an endpoint such as the endpoint 106 or a conventional device such as a telephone. If the destination is an endpoint, the endpoint 104 may have additional information regarding the endpoint 106 and may have preferences configured to control the behavior of the endpoint 104 with respect to the endpoint 106. In the present example, the call is a cellular call, but it is understood that that the call may be made over many different types of networks.

In step 3306, the endpoint 104 determines whether a request has been received from the destination for an IP communication session. For example, the endpoint 104 may receive a message over one or more of the private, public, and relay routes previously described. This may occur prior to the call of step 3304 being answered by the destination. If no IP session request has been received, the method 3300 continues to step 3308, where the call initiated in step 3304 continues. For example, the endpoint 104 may wait for the destination to answer the call normally, the call may ring until the endpoint 104 hangs up, or the call may be routed to voicemail.

If an IP session request is received as determined by step 3306, the method 3300 moves to step 3310. In step 3310, a determination may be made as to whether the IP session request is accepted by the endpoint 104. For example, the endpoint 104 may be online as seen by the endpoint 106, but may have a slower connection than is needed or desired for an IP communication session with the endpoint 104, may be on a data plan that will occur undesirable costs, or may not want to establish an IP connection for other reasons. Accordingly, even though the endpoint 104 is online and may receive the IP communication session request, the endpoint 104 may reject the request. If the endpoint 104 rejects the request, the method 3300 continues to step 3308, where the call initiated in step 3304 continues. Although not shown, the endpoint 104 may send a message to the endpoint 106 rejecting the request. In some embodiments, the endpoint 104 may be configured to automatically accept the request.

If the endpoint 104 accepts the request as determined in step 3310, the method 3300 continues to step 3312. In step 3312, a determination is made as to whether the endpoint 106 is a buddy of the endpoint 104. If the endpoint 106 is a buddy of the endpoint 104, the request received in step 3306 may be a regular message for the IP communication session and the method 3300 continues to step 3316. If the endpoint 106 is not a buddy of the endpoint 104 as determined by step 3312, the method 3300 continues to step 3314.

In the present example, a determination is made in step 3314 as to whether a temporary buddy request received from the endpoint 106 is to be approved or denied. Approval may happen automatically if the endpoint 104 is so configured. For example, the endpoint 104 may be configured to automatically approve temporary buddy requests received from an endpoint that the endpoint 104 has just dialed. If the temporary buddy request is approved, the method 3300 continues to step 3316. If the temporary buddy request is denied, the method 3300 continues to step 3308, where the call initiated in step 3304 continues. It is understood that if the endpoints 104 and 106 are buddies and either the endpoint 104 or the endpoint 106 is offline, then the call may continue in step 3308 as at least one of the endpoints will be unavailable for an IP session and there would be no request in step 3306.

It is understood that steps 3310, 3312, and 3314 may be performed in a different order, may be combined, or particular steps may be omitted in some embodiments. For example, the endpoint 104 may be configured to ignore whether the endpoint 106 is a buddy since the endpoint 104 initiated the call. In another example, the buddy check may be part of the initial request of step 3310 or the determination of step 3312.

In step 3316, the IP communication session is established with the endpoint 106. This may include identifying one or more or more of the previously described private, public, and relay routes or may involve other routing. In step 3318, the call leg for the call initiated in step 3304 is torn down, although this may happen earlier than shown.

Referring to FIG. 34, a flowchart illustrates one embodiment of a method 3400 that may represent a process by which an endpoint such as the endpoint 106 of FIG. 30 establishes a connection with the endpoint 104 as described with respect to FIG. 31 above. At the beginning of the method 3400, the endpoint 106 is active and has logged into a peer-to-peer network as previously described.

In step 3402, the endpoint 106 receives an incoming call from the endpoint 104. The call may be any type of call, but is a cellular network call for purposes of illustration. In step 3404, a determination is made as to whether the endpoint 104 is a buddy. It is understood that the endpoint 106 may not know whether the endpoint 104 is even an endpoint initially, as the incoming call is a normal cellular call. However, the endpoint 106 may match the originating number (e.g., using caller ID) against the profile downloaded from the access server 102 and determine if the originating number corresponds to a buddy of the endpoint 106. If the endpoint 104 is a buddy, the method 3400 moves to step 3410.

If the endpoint 104 is not a buddy (which may include cases where the originating number is not even an endpoint), the method 3400 moves to step 3406. In step 3406, a determination is made as to whether to send a temporary buddy request to the endpoint 104. If no temporary buddy request is to be sent, the method 3400 continues to step 3408, where the incoming call is continued. For example, the endpoint 106 may answer the incoming call. If a temporary buddy request is to be sent, the method 3400 sends the request and moves to step 3410.

It is understood that step 3406 may not occur in some embodiments. It is also understood that this step may include determining whether the originating number is associated with an endpoint. For example, the endpoint 106 may query the access server 102 for IP address information corresponding to an endpoint registered with the originating number if the endpoint 104 is not a buddy. If the access server 102 has no such number registered, the endpoint 106 may conclude that the originating number is not an endpoint. For example, the originating number may be associated with a device that is capable of endpoint functionality but is not configured as an endpoint or may be a device that is not capable of being an endpoint (e.g., a conventional telephone).

In step 3410, whether the method 3400 moves directly from step 3404 or from step 3406, a determination is made as to whether the endpoint 104 is online For example, the endpoint 104 may be a buddy but may have a status of offline. If the endpoint 104 is not online, the method 3400 continues to step 3408, where the incoming call is continued. If the endpoint 104 is online, the method 3400 continues to step 3412. In step 3412, a determination is made as to whether to send an IP communication session request to the endpoint 104. For example, the endpoint 106 may determine that an IP network currently available to the endpoint 106 is incapable of adequately supporting the IP communication session or the endpoint 104 may be configured to not make such requests due to data plan limitations or other configuration parameters. Accordingly, the endpoint 106 may not send the request even if the endpoint 104 is available. If no request is sent, the method 3400 continues to step 3408, where the incoming call is continued.

If a request for an IP communication session is to be sent as determined in step 3412, the endpoint 106 sends the request in step 3414. In step 3416, a determination may be made as to whether the request has been accepted by the endpoint 104. If the request is not accepted, the method 3400 continues to step 3408, where the incoming call is continued. If the request is accepted, the IP communication session is established with the endpoint 104 in step 3418. This may include identifying one or more or more of the previously described private, public, and relay routes or may involve other routing. In step 3420, the call leg for the call initiated in step 3304 is torn down, although this may happen earlier than shown.

Accordingly, the endpoint 104 may determine whether to send the reverse invitation of step 3414 based on one or more parameters that may be handled automatically by the endpoint or may be configured by a user. For example, signal strength of an available IP connection, time remaining on a data plan, and similar parameters may be set to handle the behavior of the endpoint 106.

It is understood that the use of a reverse invitation may provide cost savings by offloading calls from PSTN/cellular networks to IP networks in a manner that is seamless to the users of the endpoints (aside from parameters that may be user defined). For example, if the endpoint 104 is in the United States and the endpoint 106 is in England, the user of the endpoint 104 may simply dial the telephone number of the endpoint 106, including any country/regional codes. The endpoint 106 receives the incoming call and sends the reverse invitation to switch to an IP network. The endpoints 104 and 106 establish the IP communication session and their users can communicate normally without having to handle the transition themselves.

Referring to FIG. 35, a sequence diagram illustrates another embodiment of a message sequence 3500 that may occur in the environment 3000 of FIG. 30. In the present example, the endpoint 104 may request the switch to the IP network. In such embodiments, the initial request would be sent from the endpoint 104 to the endpoint 106 after the call was placed. Accordingly, FIG. 35 is similar to FIG. 31 except that step 3514 is performed by the endpoint 104 and the arrows for steps 3516 and 3518 are reversed from their counterparts in FIG. 31.

Referring to FIGS. 36A and 36B, in another embodiment, an environment 3600 is illustrated in which an endpoint (e.g., the endpoint 104 of FIG. 30) may establish communication sessions, such as a conference call or multiple separate sessions, with multiple endpoints (e.g., the endpoint 106 of FIG. 30 and an endpoint 3602). In the present example, the endpoint 104 calls the endpoint 106 as illustrated by arrow 3604 and receives a reverse invitation as illustrated by arrow 3606. This results in an IP communication session between the endpoints 104 and 106, rather than the initial call, as illustrated by arrow 3612. Similarly, the endpoint 104 calls the endpoint 3602 as illustrated by arrow 3608 and receives a reverse invitation as illustrated by arrow 3610. This results in an IP communication session between the endpoints 104 and 3602, rather than the initial call, as illustrated by arrow 3614. Accordingly, the initial call request may switched from a first network, such as a PSTN or cellular network, to a second network, such as an IP network (e.g., WiFi), before the call is established on the first network. The process of establishing the IP communication sessions 3612 and 3614 may be similar or identical to the message sequence 3100 of FIG. 31.

Referring to FIGS. 37A and 37B, in another embodiment, an environment 3700 is illustrated in which an endpoint (e.g., the endpoint 104 of FIG. 30) may establish communication sessions, such as a conference call or multiple separate sessions, with multiple endpoints (e.g., the endpoint 106 of FIG. 30 and an endpoint 3702). In the present example, the endpoint 104 calls the endpoint 106 as illustrated by arrow 3704 and receives a reverse invitation as illustrated by arrow 3706. This results in an IP communication session between the endpoints 104 and 106, rather than the initial call, as illustrated by arrow 3712. However, the endpoint 104 calls the endpoint 3702 as illustrated by arrow 3708 and, instead of receiving a reverse invitation, receives a signal indicating that the call has been answered as illustrated by arrow 3710. This results in a regular call (e.g., a cellular or PSTN based call) between the endpoints 104 and 3702 as illustrated by arrow 3714. Accordingly, for the endpoint 106, the initial call request may switched from a first network, such as a PSTN or cellular network, to a second network, such as an IP network (e.g., WiFi), before the call is established on the first network. For the endpoint 3702, the call may stay on the first network. The process of establishing the IP communication sessions 3712 may be similar or identical to the message sequence 3100 of FIG. 31, while the process of establishing the regular call 3714 may be similar or identical to the message sequence 3200 of FIG. 32.

It is understood that the reverse invitation process described herein may be used to provide various services to the endpoints 104 and 106. For example, the network and/or protocol supporting the initial call may not provide for video data, such as streaming video information. The reverse invitation may be used to seamlessly switch the call to an IP network that can support streaming video, thereby not only providing cost savings in some cases, but also expanding the services that may be provided. In some embodiments, signaling may occur over the original call channel, while data may be transferred via the reverse invitation channel.

The reverse invitation process described herein relies on presence awareness. For example, the endpoint 106 needs presence information about the endpoint 104 before the endpoint 106 can send the reverse invitation to the endpoint 104. While the preceding reverse invitation embodiments use a presence model based on direct presence notification as described, for example, with respect to step 410 of FIG. 4, other presence models may be used. For example, in some embodiments, the direct peer-to-peer communication of presence information between endpoints such as the endpoints 104 and 106 of FIG. 30 may be unavailable. In such cases, endpoints may not be allowed to directly communicate, may be in different parts of a network or in different networks, or other reasons may prevent direct presence notifications. Alternatively or additionally, the endpoints may be configured to leverage existing network architectures and services to obtain presence information. An enterprise network, for example, may treat all devices in a similar manner and may provide presence information to all devices within the enterprise network rather than allowing some devices to directly notify others of their online status as described with respect to FIG. 4.

Accordingly, it is understood that presence information may be obtained in many different ways, including through system architectures having presence notification functions included therein. For example, in one embodiment, an endpoint may obtain presence information via a subscribe/publish/notify model as described in detail in RFC 3265, which is incorporated herein by reference in its entirety. In another example, an endpoint may obtain presence information via a query model as described in detail in RFC 3680, which is incorporated herein by reference in its entirety. Although these examples use SIP as a messaging protocol, it is understood that presence may be obtained using messaging other than SIP. Accordingly, once presence information is obtained, the reverse invitation process may occur as described above without regard for how the presence information was obtained. For example, the endpoint 106 may receive the incoming call from the endpoint 104 and communicate with the system (e.g., a PBX or other system component) to determine a presence status of the endpoint 104. The endpoint 106 may then continue as described previously after obtaining information that the endpoint 104 is available or unavailable.

In some embodiments, calling patterns may be used to determine where to store information. For example, the endpoint 104 may store frequently called numbers and information corresponding to those numbers in the endpoint's memory, while less frequently called numbers and information corresponding to those numbers is stored elsewhere, such as on the access server 102. This allows optimization to occur without the need for the endpoint 104 to look up all information and also without the need to store all information on the endpoint 104.

Referring to FIG. 38, one embodiment of a computer system 3800 is illustrated. The computer system 3800 is one possible example of a system component or device such as an endpoint, an access server, or a shadow server. The computer system 3800 may include a central processing unit (“CPU”) 3802, a memory unit 3804, an input/output (“I/O”) device 3806, and a network interface 3808. The components 3802, 3804, 3806, and 3808 are interconnected by a transport system (e.g., a bus) 3810. A power supply (PS) 3812 may provide power to components of the computer system 3800, such as the CPU 3802 and memory unit 3804. It is understood that the computer system 3800 may be differently configured and that each of the listed components may actually represent several different components. For example, the CPU 3802 may actually represent a multi-processor or a distributed processing system; the memory unit 3804 may include different levels of cache memory, main memory, hard disks, and remote storage locations; the I/O device 3806 may include monitors, keyboards, and the like; and the network interface 3808 may include one or more network cards providing one or more wired and/or wireless connections to the packet network 108 (FIG. 1). Therefore, a wide range of flexibility is anticipated in the configuration of the computer system 3800.

The computer system 3800 may use any operating system (or multiple operating systems), including various versions of operating systems provided by Microsoft (such as WINDOWS), Apple (such as Mac OS X), UNIX, and LINUX, and may include operating systems specifically developed for handheld devices, personal computers, and servers depending on the use of the computer system 3800. The operating system, as well as other instructions (e.g., for the endpoint engine 252 of FIG. 2 if an endpoint), may be stored in the memory unit 3804 and executed by the processor 3802. For example, if the computer system 3800 is the endpoint 104, the memory unit 3804 may include instructions for performing the methods described with respect to FIGS. 33 and 34.

Accordingly, in one embodiment, a method for a reverse invitation comprises receiving, by a first endpoint, an inbound call from a second endpoint, wherein the inbound call is received via one of a cellular network and a public switched telephone network; sending, by the first endpoint, an invitation message to the second endpoint via an Internet Protocol (IP) peer-to-peer network in response to the inbound call, wherein the invitation message requests that the second endpoint establish a peer-to-peer communication session with the first endpoint via the peer-to-peer network; determining, by the first endpoint, whether an acknowledgement message has been received from the second endpoint in response to the invitation message; and continuing, by the first endpoint, the inbound call with the second endpoint on the one of the cellular network and the public switched telephone network on which the inbound call was received if the acknowledgement message has not been received by the first endpoint. The method may further comprise establishing, by the first endpoint, the peer-to-peer communication session with the second endpoint if the acknowledgement message has been received by the first endpoint; and releasing, by the first endpoint, resources of the first endpoint reserved for the inbound call on the one of the cellular network and the public switched telephone network. The method may further comprise determining, by the first endpoint, whether the second point is available via the peer-to-peer network prior to sending the invitation message to the second endpoint. The determining whether the second point is available may occur based on a presence notification sent directly between the first endpoint and the second endpoint. The determining whether the second point is available may occur by obtaining, by the first endpoint, presence information of the second endpoint from a system accessible to the first endpoint. The method may further comprise determining, by the first endpoint, whether the second endpoint is a buddy of the first endpoint prior to sending the invitation message to the second endpoint. The determining whether the second endpoint is a buddy of the first endpoint may be based on an E.164 number corresponding to the second endpoint, wherein the first endpoint extracts the E.164 number of the second endpoint from the inbound call. The first endpoint may read the E.164 number in reverse order and any digits past ten may be viewed by the first endpoint as one of a country code and a region code. The determining whether the second endpoint is a buddy of the first endpoint may be based on one of an Electronic Serial Number (ESN) and an International Mobile Equipment Identity (IMEI) number corresponding to the second endpoint. The method may further comprise sending, by the first endpoint, a temporary buddy request to the second endpoint if the second endpoint is not a buddy of the first endpoint, wherein the temporary buddy request establishes a buddy relationship between the first and second endpoints for the duration of the peer-to-peer communication session. The method may further comprise sending, by the first endpoint, a information request message to an access server of the peer-to-peer network if the second endpoint is not a buddy of the first endpoint; and receiving, by the first endpoint, address information of the second endpoint from the access server. The method may further comprise determining, by the first endpoint, that an IP network providing access for the first endpoint for the peer-to-peer communication session is capable of supporting the peer-to-peer communication session prior to sending the invitation message. The method may further comprise formatting, by the first endpoint, the invitation message as a Session Initiation Protocol (SIP) message.

In another embodiment, a method for establishing a communication session by a first endpoint comprises receiving, by the first endpoint, a first plurality of digits identifying a first destination device; initiating, by the first endpoint, an outbound call to the first destination device based on the first plurality of digits, wherein the outbound call is initiated via one of a cellular network and a public switched telephone network; receiving, by the first endpoint, an invitation message from the first destination device via an Internet Protocol (IP) peer-to-peer network, wherein the invitation message requests that the first endpoint establish a peer-to-peer communication session with the first destination device; sending, by the first endpoint, an acknowledgement message to the first destination device in response to the invitation message; establishing, by the first endpoint, the peer-to-peer communication session with the first destination device; and releasing, by the first endpoint, resources of the first endpoint reserved for the outbound call via the one of the cellular network and the public switched telephone network. The method may further comprise determining, by the first endpoint, whether to accept the request for the peer-to-peer communication session with the first destination device. The request may be automatically accepted by the first endpoint. The method may further comprise determining, by the first endpoint, whether the first destination device is a second endpoint that is a buddy. The step of determining whether to accept the request for the peer-to-peer communication session may include determining that an IP network providing access for the first endpoint for the peer-to-peer communication session is capable of supporting the peer-to-peer communication session. The method may further comprise receiving, by the first endpoint, a second plurality of digits identifying a second destination device; initiating, by the first endpoint, an outbound call to the second destination device based on the second plurality of digits, wherein the outbound call is initiated via one of the cellular network and the public switched telephone network; receiving, by the first endpoint, an indication that the second destination device has answered the outbound call; and maintaining, by the first endpoint, the outbound call with the second destination device via the one of the cellular network and the public switched telephone network, wherein the outbound call with the second destination device via the one of the cellular network and the public switched telephone network is supported by the first endpoint simultaneously with the peer-to-peer communication session with the first destination device. The method may further comprise coupling, by the first endpoint, the outbound call with the second destination device via the one of the cellular network and the public switched telephone network and the peer-to-peer communication session with the first destination device.

In still another embodiment, an endpoint comprises a network interface configured to send and receive communications via at least first and second networks, wherein the first network is one of a cellular network and a public switched telephone network and the second network is an internet protocol (IP) based peer-to-peer network; a controller coupled to the network interface; and a memory coupled to the controller, the memory having a plurality of instructions stored thereon for execution by the controller, the instructions including instructions for: receiving an inbound call from a calling endpoint via the first network; identifying that the calling endpoint is accessible via the second network; sending an invitation message to the calling endpoint via the second network in response to the inbound call, wherein the invitation message requests that the calling endpoint establish a peer-to-peer communication session via the second network; establishing the peer-to-peer communication session with the calling endpoint; and releasing resources reserved for the inbound call. The endpoint may further comprise instructions for determining whether an acknowledgement message has been received from the second endpoint in response to the invitation message. The endpoint may further comprise instructions for determining that the second network is capable of supporting the peer-to-peer communication session prior to sending the invitation message. The endpoint may be a mobile handset. The endpoint may include an E.164 number that is used by the calling endpoint to initiate the inbound call. The peer-to-peer communication session may be established via Session Initiation Protocol (SIP) signaling.

While the preceding description shows and describes one or more embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present disclosure. For example, various steps illustrated within a particular sequence diagram or flow chart may be combined or further divided. In addition, steps described in one diagram or flow chart may be incorporated into another diagram or flow chart. Furthermore, the described functionality may be provided by hardware and/or software, and may be distributed or combined into a single platform. Additionally, functionality described in a particular example may be achieved in a manner different than that illustrated, but is still encompassed within the present disclosure. Therefore, the claims should be interpreted in a broad manner, consistent with the present disclosure. 

1. A method for a reverse invitation comprising: receiving, by a first endpoint, an inbound call from a second endpoint, wherein the inbound call is received via one of a cellular network and a public switched telephone network; sending, by the first endpoint, an invitation message to the second endpoint via an Internet Protocol (IP) peer-to-peer network in response to the inbound call, wherein the invitation message requests that the second endpoint establish a peer-to-peer communication session with the first endpoint via the peer-to-peer network; determining, by the first endpoint, whether an acknowledgement message has been received from the second endpoint in response to the invitation message; and continuing, by the first endpoint, the inbound call with the second endpoint on the one of the cellular network and the public switched telephone network on which the inbound call was received if the acknowledgement message has not been received by the first endpoint.
 2. The method of claim 1 further comprising: establishing, by the first endpoint, the peer-to-peer communication session with the second endpoint if the acknowledgement message has been received by the first endpoint; and releasing, by the first endpoint, resources of the first endpoint reserved for the inbound call on the one of the cellular network and the public switched telephone network.
 3. The method of claim 1 further comprising determining, by the first endpoint, whether the second point is available via the peer-to-peer network prior to sending the invitation message to the second endpoint.
 4. The method of claim 3 wherein the determining whether the second point is available occurs based on a presence notification sent directly between the first endpoint and the second endpoint.
 5. The method of claim 3 wherein the determining whether the second point is available occurs by obtaining, by the first endpoint, presence information of the second endpoint from a system accessible to the first endpoint.
 6. The method of claim 1 further comprising determining, by the first endpoint, whether the second endpoint is a buddy of the first endpoint prior to sending the invitation message to the second endpoint.
 7. The method of claim 6 wherein the determining whether the second endpoint is a buddy of the first endpoint is based on an E.164 number corresponding to the second endpoint, wherein the first endpoint extracts the E.164 number of the second endpoint from the inbound call.
 8. The method of claim 7 wherein the first endpoint reads the E.164 number in reverse order and wherein any digits past ten are viewed by the first endpoint as one of a country code and a region code.
 9. The method of claim 6 wherein the determining whether the second endpoint is a buddy of the first endpoint is based on one of an Electronic Serial Number (ESN) and an International Mobile Equipment Identity (IMEI) number corresponding to the second endpoint.
 10. The method of claim 6 further comprising sending, by the first endpoint, a temporary buddy request to the second endpoint if the second endpoint is not a buddy of the first endpoint, wherein the temporary buddy request establishes a buddy relationship between the first and second endpoints for the duration of the peer-to-peer communication session.
 11. The method of claim 10 further comprising: sending, by the first endpoint, a information request message to an access server of the peer-to-peer network if the second endpoint is not a buddy of the first endpoint; and receiving, by the first endpoint, address information of the second endpoint from the access server.
 12. The method of claim 1 further comprising determining, by the first endpoint, that an IP network providing access for the first endpoint for the peer-to-peer communication session is capable of supporting the peer-to-peer communication session prior to sending the invitation message.
 13. The method of claim 1 further comprising formatting, by the first endpoint, the invitation message as a Session Initiation Protocol (SIP) message.
 14. A method for establishing a communication session by a first endpoint comprising: receiving, by the first endpoint, a first plurality of digits identifying a first destination device; initiating, by the first endpoint, an outbound call to the first destination device based on the first plurality of digits, wherein the outbound call is initiated via one of a cellular network and a public switched telephone network; receiving, by the first endpoint, an invitation message from the first destination device via an Internet Protocol (IP) peer-to-peer network, wherein the invitation message requests that the first endpoint establish a peer-to-peer communication session with the first destination device; sending, by the first endpoint, an acknowledgement message to the first destination device in response to the invitation message; establishing, by the first endpoint, the peer-to-peer communication session with the first destination device; and releasing, by the first endpoint, resources of the first endpoint reserved for the outbound call via the one of the cellular network and the public switched telephone network.
 15. The method of claim 14 further comprising determining, by the first endpoint, whether to accept the request for the peer-to-peer communication session with the first destination device.
 16. The method of claim 15 wherein the request is automatically accepted by the first endpoint.
 17. The method of claim 15 further comprising determining, by the first endpoint, whether the first destination device is a second endpoint that is a buddy.
 18. The method of claim 15 wherein the step of determining whether to accept the request for the peer-to-peer communication session includes determining that an IP network providing access for the first endpoint for the peer-to-peer communication session is capable of supporting the peer-to-peer communication session.
 19. The method of claim 14 further comprising: receiving, by the first endpoint, a second plurality of digits identifying a second destination device; initiating, by the first endpoint, an outbound call to the second destination device based on the second plurality of digits, wherein the outbound call is initiated via one of the cellular network and the public switched telephone network; receiving, by the first endpoint, an indication that the second destination device has answered the outbound call; and maintaining, by the first endpoint, the outbound call with the second destination device via the one of the cellular network and the public switched telephone network, wherein the outbound call with the second destination device via the one of the cellular network and the public switched telephone network is supported by the first endpoint simultaneously with the peer-to-peer communication session with the first destination device.
 20. The method of claim 19 further comprising coupling, by the first endpoint, the outbound call with the second destination device via the one of the cellular network and the public switched telephone network and the peer-to-peer communication session with the first destination device.
 21. An endpoint comprising: a network interface configured to send and receive communications via at least first and second networks, wherein the first network is one of a cellular network and a public switched telephone network and the second network is an internet protocol (IP) based peer-to-peer network; a controller coupled to the network interface; and a memory coupled to the controller, the memory having a plurality of instructions stored thereon for execution by the controller, the instructions including instructions for: receiving an inbound call from a calling endpoint via the first network; identifying that the calling endpoint is accessible via the second network; sending an invitation message to the calling endpoint via the second network in response to the inbound call, wherein the invitation message requests that the calling endpoint establish a peer-to-peer communication session via the second network; establishing the peer-to-peer communication session with the calling endpoint; and releasing resources reserved for the inbound call.
 22. The endpoint of claim 21 further comprising instructions for determining whether an acknowledgement message has been received from the second endpoint in response to the invitation message.
 23. The endpoint of claim 21 further comprising instructions for determining that the second network is capable of supporting the peer-to-peer communication session prior to sending the invitation message.
 24. The endpoint of claim 21 wherein the endpoint is a mobile handset.
 25. The endpoint of claim 24 wherein the endpoint includes an E.164 number that is used by the calling endpoint to initiate the inbound call.
 26. The endpoint of claim 25 wherein the peer-to-peer communication session is established via Session Initiation Protocol (SIP) signaling. 